diff --git a/easybuild/base/exceptions.py b/easybuild/base/exceptions.py
index e7adbc496c..007b14ed7f 100644
--- a/easybuild/base/exceptions.py
+++ b/easybuild/base/exceptions.py
@@ -34,10 +34,12 @@
 import logging
 import os
 
+from typing import Optional, List
+
 from easybuild.base import fancylogger
 
 
-def get_callers_logger():
+def get_callers_logger() -> Optional[logging.Logger]:
     """
     Get logger defined in caller's environment
     :return: logger instance (or None if none was found)
@@ -76,11 +78,11 @@ class LoggedException(Exception):
     # must accept an argument of type string, i.e. the log message, and an optional list of formatting arguments
     LOGGING_METHOD_NAME = 'error'
     # list of top-level package names to use to format location info; None implies not to include location info
-    LOC_INFO_TOP_PKG_NAMES = []
+    LOC_INFO_TOP_PKG_NAMES: List[str] = []
     # include location where error was raised from (enabled by default under 'python', disabled under 'python -O')
     INCLUDE_LOCATION = __debug__
 
-    def __init__(self, msg, *args, **kwargs):
+    def __init__(self, msg: str, *args, **kwargs) -> None:
         """
         Constructor.
         :param msg: exception message
@@ -91,7 +93,7 @@ def __init__(self, msg, *args, **kwargs):
         if args:
             msg = msg % args
 
-        backtrace = []
+        backtrace: List[str] = []
         if self.LOC_INFO_TOP_PKG_NAMES is not None:
             # determine correct frame to fetch location information from
             frames_up = 1
diff --git a/easybuild/base/frozendict.py b/easybuild/base/frozendict.py
index 06ad117c99..62bf6fd0e0 100644
--- a/easybuild/base/frozendict.py
+++ b/easybuild/base/frozendict.py
@@ -23,6 +23,7 @@
 import operator
 from collections.abc import Mapping
 from functools import reduce
+from typing import List
 
 from easybuild.base import fancylogger
 
@@ -64,8 +65,7 @@ def keys(self):
 class FrozenDictKnownKeys(FrozenDict):
     """A frozen dictionary only allowing known keys."""
 
-    # list of known keys
-    KNOWN_KEYS = []
+    KNOWN_KEYS: List[str] = []
 
     def __init__(self, *args, **kwargs):
         """Constructor, only way to define the contents."""
diff --git a/easybuild/base/generaloption.py b/easybuild/base/generaloption.py
index f0db658f3b..62bd8162d5 100644
--- a/easybuild/base/generaloption.py
+++ b/easybuild/base/generaloption.py
@@ -45,6 +45,7 @@
 from io import StringIO
 from optparse import Option, OptionGroup, OptionParser, OptionValueError, Values
 from optparse import SUPPRESS_HELP as nohelp  # supported in optparse of python v2.4
+from typing import List
 
 from easybuild.base.fancylogger import getLogger, setroot, setLogLevel, getDetailsLogLevels
 from easybuild.base.optcomplete import autocomplete, CompleterOption
@@ -905,9 +906,10 @@ class GeneralOption:
     INTERSPERSED = True  # mix args with options
 
     CONFIGFILES_USE = True
-    CONFIGFILES_RAISE_MISSING = False
-    CONFIGFILES_INIT = []  # initial list of defaults, overwritten by go_configfiles options
-    CONFIGFILES_IGNORE = []
+    CONFIGFILES_RAISE_MISSING: bool = False
+    # initial list of defaults, overwritten by go_configfiles options
+    CONFIGFILES_INIT: List[str] = []
+    CONFIGFILES_IGNORE: List[str] = []
     CONFIGFILES_MAIN_SECTION = 'MAIN'  # sectionname that contains the non-grouped/non-prefixed options
     CONFIGFILE_CASESENSITIVE = True
 
diff --git a/easybuild/framework/easyconfig/easyconfig.py b/easybuild/framework/easyconfig/easyconfig.py
index 698891a772..9380182ca8 100644
--- a/easybuild/framework/easyconfig/easyconfig.py
+++ b/easybuild/framework/easyconfig/easyconfig.py
@@ -48,7 +48,7 @@
 import re
 from collections import OrderedDict
 from contextlib import contextmanager
-from typing import Optional
+from typing import Any, Dict, Optional
 
 import easybuild.tools.filetools as filetools
 from easybuild.base import fancylogger
@@ -111,9 +111,9 @@
     HAVE_AUTOPEP8 = False
 
 
-_easyconfig_files_cache = {}
-_easyconfigs_cache = {}
-_path_indexes = {}
+_easyconfig_files_cache: Dict[str, Any] = {}
+_easyconfigs_cache: Dict[str, Any] = {}
+_path_indexes: Dict[str, int] = {}
 
 
 def handle_deprecated_or_replaced_easyconfig_parameters(ec_method):
diff --git a/easybuild/framework/easyconfig/format/one.py b/easybuild/framework/easyconfig/format/one.py
index acd1af6f6c..e0a6f3f32c 100644
--- a/easybuild/framework/easyconfig/format/one.py
+++ b/easybuild/framework/easyconfig/format/one.py
@@ -37,6 +37,7 @@
 import pprint
 import re
 import tempfile
+from typing import List
 
 from easybuild.base import fancylogger
 from easybuild.framework.easyconfig.format.format import DEPENDENCY_PARAMETERS, EXCLUDED_KEYS_REPLACE_TEMPLATES
@@ -100,7 +101,7 @@ class FormatOneZero(EasyConfigFormatConfigObj):
 
     PYHEADER_ALLOWED_BUILTINS = None  # allow all
     PYHEADER_MANDATORY = ['version', 'name', 'toolchain', 'homepage', 'description']
-    PYHEADER_BLACKLIST = []
+    PYHEADER_BLACKLIST: List[str] = []
 
     def __init__(self, *args, **kwargs):
         """FormatOneZero constructor."""
diff --git a/easybuild/framework/easyconfig/format/pyheaderconfigobj.py b/easybuild/framework/easyconfig/format/pyheaderconfigobj.py
index 782aaa5fec..ab12035f67 100644
--- a/easybuild/framework/easyconfig/format/pyheaderconfigobj.py
+++ b/easybuild/framework/easyconfig/format/pyheaderconfigobj.py
@@ -34,6 +34,7 @@
 import copy
 import re
 import sys
+from typing import List
 
 from easybuild.base import fancylogger
 from easybuild.framework.easyconfig.constants import EASYCONFIG_CONSTANTS
@@ -152,7 +153,7 @@ class EasyConfigFormatConfigObj(EasyConfigFormat):
      - feed to ConfigObj
     """
 
-    PYHEADER_ALLOWED_BUILTINS = []  # default no builtins
+    PYHEADER_ALLOWED_BUILTINS: List[str] = []  # default no builtins
     PYHEADER_MANDATORY = None  # no defaults
     PYHEADER_BLACKLIST = None  # no defaults
 
diff --git a/easybuild/scripts/rpath_args.py b/easybuild/scripts/rpath_args.py
index 0a15d9ede1..d63b9cce4e 100755
--- a/easybuild/scripts/rpath_args.py
+++ b/easybuild/scripts/rpath_args.py
@@ -37,6 +37,7 @@
 import re
 import sys
 
+
 LINKER_COMMANDS = (
     # binutils
     'ld', 'ld.gold', 'ld.bfd',
diff --git a/easybuild/toolchains/compiler/clang.py b/easybuild/toolchains/compiler/clang.py
index 73d48ddf92..3d2595293a 100644
--- a/easybuild/toolchains/compiler/clang.py
+++ b/easybuild/toolchains/compiler/clang.py
@@ -34,6 +34,8 @@
 """
 
 import easybuild.tools.systemtools as systemtools
+from typing import List
+
 from easybuild.tools.toolchain.compiler import Compiler
 
 
@@ -104,7 +106,7 @@ class Clang(Compiler):
 
     COMPILER_CC = 'clang'
     COMPILER_CXX = 'clang++'
-    COMPILER_C_UNIQUE_OPTIONS = []
+    COMPILER_C_UNIQUE_OPTIONS: List[str] = []
 
     LIB_MULTITHREAD = ['pthread']
     LIB_MATH = ['m']
diff --git a/easybuild/toolchains/compiler/cuda.py b/easybuild/toolchains/compiler/cuda.py
index 2bcdf294cf..0a41555f03 100644
--- a/easybuild/toolchains/compiler/cuda.py
+++ b/easybuild/toolchains/compiler/cuda.py
@@ -30,6 +30,8 @@
 * Kenneth Hoste (Ghent University)
 """
 
+from typing import Dict, List, Tuple
+
 from easybuild.tools.toolchain.compiler import Compiler
 
 
@@ -42,7 +44,7 @@ class Cuda(Compiler):
     COMPILER_CUDA_MODULE_NAME = ['CUDA']
     COMPILER_CUDA_FAMILY = TC_CONSTANT_CUDA
 
-    COMPILER_CUDA_UNIQUE_OPTS = {
+    COMPILER_CUDA_UNIQUE_OPTS: Dict[str, Tuple[List[str], str]] = {
         # handle '-gencode arch=X,code=Y' nvcc options (also -arch, -code)
         # -arch always needs to be specified, -code is optional (defaults to -arch if missing)
         # -gencode is syntactic sugar for combining -arch/-code
diff --git a/easybuild/toolchains/compiler/gcc.py b/easybuild/toolchains/compiler/gcc.py
index dda45b5507..2daf5b08ea 100644
--- a/easybuild/toolchains/compiler/gcc.py
+++ b/easybuild/toolchains/compiler/gcc.py
@@ -32,6 +32,7 @@
 """
 
 import re
+from typing import List
 
 import easybuild.tools.systemtools as systemtools
 from easybuild.tools import LooseVersion
@@ -118,7 +119,7 @@ class Gcc(Compiler):
 
     COMPILER_CC = 'gcc'
     COMPILER_CXX = 'g++'
-    COMPILER_C_UNIQUE_OPTIONS = []
+    COMPILER_C_UNIQUE_OPTIONS: List[str] = []
 
     COMPILER_F77 = 'gfortran'
     COMPILER_F90 = 'gfortran'
diff --git a/easybuild/tools/asyncprocess.py b/easybuild/tools/asyncprocess.py
index 2dc2f840f4..ec20977222 100644
--- a/easybuild/tools/asyncprocess.py
+++ b/easybuild/tools/asyncprocess.py
@@ -73,6 +73,7 @@
 import select
 import subprocess
 import time
+from typing import Any, Optional, Tuple, Union
 
 PIPE = subprocess.PIPE
 STDOUT = subprocess.STDOUT
@@ -88,27 +89,28 @@ def __init__(self, *args, **kwargs):
         kwargs['bufsize'] = 0
         super().__init__(*args, **kwargs)
 
-    def recv(self, maxsize=None):
+    def recv(self, maxsize: Optional[int] = None) -> Optional[Union[str, bytes]]:
         return self._recv('stdout', maxsize)
 
-    def recv_err(self, maxsize=None):
+    def recv_err(self, maxsize: Optional[int] = None) -> Optional[Union[str, bytes]]:
         return self._recv('stderr', maxsize)
 
-    def send_recv(self, inp='', maxsize=None):
+    def send_recv(self, inp: str = '', maxsize: Optional[int] = None) -> Tuple[
+            Optional[int], Optional[Union[str, bytes]], Optional[Union[str, bytes]]]:
         return self.send(inp), self.recv(maxsize), self.recv_err(maxsize)
 
-    def get_conn_maxsize(self, which, maxsize):
+    def get_conn_maxsize(self, which: str, maxsize: Optional[int]) -> Tuple[Any, int]:
         if maxsize is None:
             maxsize = 1024
         elif maxsize < 1:
             maxsize = 1
         return getattr(self, which), maxsize
 
-    def _close(self, which):
+    def _close(self, which: str) -> None:
         getattr(self, which).close()
         setattr(self, which, None)
 
-    def send(self, inp):
+    def send(self, inp: str) -> Optional[int]:
         if not self.stdin:
             return None
 
@@ -124,7 +126,7 @@ def send(self, inp):
 
         return written
 
-    def _recv(self, which, maxsize):
+    def _recv(self, which: str, maxsize: Optional[int]) -> Optional[Union[str, bytes]]:
         conn, maxsize = self.get_conn_maxsize(which, maxsize)
         if conn is None:
             return None
@@ -152,7 +154,7 @@ def _recv(self, which, maxsize):
 message = "Other end disconnected!"
 
 
-def recv_some(p, t=.2, e=1, tr=5, stderr=0):
+def recv_some(p: 'Popen', t: float = 0.2, e: int = 1, tr: int = 5, stderr: int = 0) -> bytes:
     if tr < 1:
         tr = 1
     x = time.time() + t
@@ -175,7 +177,7 @@ def recv_some(p, t=.2, e=1, tr=5, stderr=0):
     return b''.join(y)
 
 
-def send_all(p, data):
+def send_all(p: 'Popen', data: str) -> None:
     while len(data):
         sent = p.send(data)
         if sent is None:
diff --git a/easybuild/tools/build_details.py b/easybuild/tools/build_details.py
index e9b74cb564..c6d4414719 100644
--- a/easybuild/tools/build_details.py
+++ b/easybuild/tools/build_details.py
@@ -37,7 +37,7 @@
 from easybuild.tools.version import EASYBLOCKS_VERSION, FRAMEWORK_VERSION
 
 
-def get_build_stats(app, start_time, command_line):
+def get_build_stats(app, start_time: float, command_line: str) -> OrderedDict:
     """
     Return build statistics for this build
     """
diff --git a/easybuild/tools/build_log.py b/easybuild/tools/build_log.py
index e6a5103c27..385099fb2f 100644
--- a/easybuild/tools/build_log.py
+++ b/easybuild/tools/build_log.py
@@ -42,6 +42,7 @@
 from copy import copy
 from datetime import datetime, timezone
 from enum import IntEnum
+from typing import Any, Optional, Tuple
 
 from easybuild.base import fancylogger
 from easybuild.base.exceptions import LoggedException
@@ -130,7 +131,7 @@ class EasyBuildError(LoggedException):
     # always include location where error was raised from, even under 'python -O'
     INCLUDE_LOCATION = True
 
-    def __init__(self, msg, *args, exit_code=EasyBuildExit.ERROR, **kwargs):
+    def __init__(self, msg: str, *args, exit_code: EasyBuildExit = EasyBuildExit.ERROR, **kwargs) -> None:
         """Constructor: initialise EasyBuildError instance."""
         if args:
             msg = msg % args
@@ -143,12 +144,12 @@ def __str__(self):
         return self.msg
 
 
-def raise_easybuilderror(msg, *args):
+def raise_easybuilderror(msg: str, *args) -> None:
     """Raise EasyBuildError with given message, formatted by provided string arguments."""
     raise EasyBuildError(msg, *args)
 
 
-def raise_nosupport(msg, ver):
+def raise_nosupport(msg: str, ver: str) -> None:
     """Construct error message for no longer supported behaviour, and raise an EasyBuildError."""
     nosupport_msg = "NO LONGER SUPPORTED since v%s: %s; see %s for more information"
     raise_easybuilderror(nosupport_msg, ver, msg, DEPRECATED_DOC_URL)
@@ -220,7 +221,7 @@ def nosupport(self, msg, ver):
         """Raise error message for no longer supported behaviour."""
         raise_nosupport(msg, ver)
 
-    def error(self, msg, *args, **kwargs):
+    def error(self, msg: str, *args, **kwargs) -> None:
         """Print error message."""
         ebmsg = "EasyBuild encountered an error"
         # Don't show caller info when error is raised from within LoggedException.__init__
@@ -232,11 +233,11 @@ def error(self, msg, *args, **kwargs):
 
         fancylogger.FancyLogger.error(self, f"{ebmsg}: {msg}", *args, **kwargs)
 
-    def devel(self, msg, *args, **kwargs):
+    def devel(self, msg: str, *args, **kwargs) -> None:
         """Print development log message"""
         self.log(DEVEL_LOG_LEVEL, msg, *args, **kwargs)
 
-    def exception(self, msg, *args):
+    def exception(self, msg: str, *args) -> None:
         """Print exception message and raise EasyBuildError."""
         # don't raise the exception from within error
         ebmsg = "EasyBuild encountered an exception %s: " % self.caller_info()
@@ -261,7 +262,8 @@ def exception(self, msg, *args):
 _init_easybuildlog = fancylogger.getLogger(fname=False)
 
 
-def init_logging(logfile, logtostdout=False, silent=False, colorize=fancylogger.Colorize.AUTO, tmp_logdir=None):
+def init_logging(logfile: Optional[str], logtostdout: bool = False, silent: bool = False,
+                 colorize=fancylogger.Colorize.AUTO, tmp_logdir: Optional[str] = None) -> Tuple:
     """Initialize logging."""
     if logtostdout:
         fancylogger.logToScreen(enable=True, stdout=True, colorize=colorize)
@@ -286,7 +288,7 @@ def init_logging(logfile, logtostdout=False, silent=False, colorize=fancylogger.
     return log, logfile
 
 
-def log_start(log, eb_command_line, eb_tmpdir):
+def log_start(log: Any, eb_command_line: list, eb_tmpdir: str) -> None:
     """Log startup info."""
     log.info(this_is_easybuild())
 
@@ -296,7 +298,7 @@ def log_start(log, eb_command_line, eb_tmpdir):
     log.info("Using %s as temporary directory", eb_tmpdir)
 
 
-def stop_logging(logfile, logtostdout=False):
+def stop_logging(logfile: Optional[str], logtostdout: bool = False) -> None:
     """Stop logging."""
     if logtostdout:
         fancylogger.logToScreen(enable=False, stdout=True)
@@ -304,7 +306,7 @@ def stop_logging(logfile, logtostdout=False):
         fancylogger.logToFile(logfile, enable=False)
 
 
-def print_msg(msg, *args, **kwargs):
+def print_msg(msg: str, *args, **kwargs) -> None:
     """
     Print a message.
 
@@ -351,7 +353,7 @@ def print_msg(msg, *args, **kwargs):
             sys.stdout.write(msg)
 
 
-def dry_run_set_dirs(prefix, builddir, software_installdir, module_installdir):
+def dry_run_set_dirs(prefix: str, builddir: str, software_installdir: str, module_installdir: str) -> None:
     """
     Initialize for printing dry run messages.
 
@@ -372,7 +374,7 @@ def dry_run_set_dirs(prefix, builddir, software_installdir, module_installdir):
     DRY_RUN_SOFTWARE_INSTALL_DIR = (re.compile(re.escape(software_installdir)), software_installdir[len(prefix):])
 
 
-def dry_run_msg(msg, *args, **kwargs):
+def dry_run_msg(msg: str, *args, **kwargs) -> None:
     """Print dry run message."""
     # replace fake build/install dir in dry run message with original value
     if args:
@@ -389,7 +391,7 @@ def dry_run_msg(msg, *args, **kwargs):
     print_msg(msg, silent=silent, prefix=False)
 
 
-def dry_run_warning(msg, *args, **kwargs):
+def dry_run_warning(msg: str, *args, **kwargs) -> None:
     """Print dry run message."""
     if args:
         msg = msg % args
@@ -401,7 +403,7 @@ def dry_run_warning(msg, *args, **kwargs):
     dry_run_msg("\n!!!\n!!! WARNING: %s\n!!!\n" % msg, silent=silent)
 
 
-def print_error(msg, *args, **kwargs):
+def print_error(msg: str, *args, **kwargs) -> None:
     """
     Print error message and exit EasyBuild
     """
@@ -433,7 +435,7 @@ def print_error(msg, *args, **kwargs):
         raise EasyBuildError(msg)  # Handle legacy weirdness
 
 
-def print_error_and_exit(msg, *args, exit_code=EasyBuildExit.ERROR, silent=False):
+def print_error_and_exit(msg: str, *args, exit_code: EasyBuildExit = EasyBuildExit.ERROR, silent: bool = False) -> None:
     """
     Print error message and exit EasyBuild, supports format strings
 
@@ -449,7 +451,7 @@ def print_error_and_exit(msg, *args, exit_code=EasyBuildExit.ERROR, silent=False
     sys.exit(int(exit_code))
 
 
-def print_warning(msg, *args, **kwargs):
+def print_warning(msg: str, *args, **kwargs) -> None:
     """
     Print warning message.
     """
@@ -467,7 +469,7 @@ def print_warning(msg, *args, **kwargs):
         sys.stderr.write("\nWARNING: %s\n\n" % msg)
 
 
-def time_str_since(start_time):
+def time_str_since(start_time: datetime) -> str:
     """
     Return string representing amount of time that has passed since specified timestamp
 
diff --git a/easybuild/tools/bwrap.py b/easybuild/tools/bwrap.py
index 8cfd8c8cd2..7240b42b7e 100644
--- a/easybuild/tools/bwrap.py
+++ b/easybuild/tools/bwrap.py
@@ -32,6 +32,7 @@
 """
 import json
 import os
+from typing import Any
 
 from easybuild.base import fancylogger
 from easybuild.tools.build_log import EasyBuildError, print_msg
@@ -66,7 +67,7 @@ def get_bwrap_info(key):
         raise EasyBuildError(f"Unknown key specified to get bwrap info: {key}")
 
 
-def set_bwrap_info(key, value):
+def set_bwrap_info(key: str, value: Any) -> None:
     """
     Set specified info w.r.t. use of bwrap
     """
@@ -76,7 +77,7 @@ def set_bwrap_info(key, value):
         raise EasyBuildError(f"Unknown key specified to set bwrap info: {key}")
 
 
-def update_bwrap_info(key, value):
+def update_bwrap_info(key: str, value: Any) -> None:
     """
     Update specified info w.r.t. use of bwrap (only supports 'set' values currently)
     """
@@ -90,7 +91,7 @@ def update_bwrap_info(key, value):
         raise EasyBuildError(f"Unknown key specified to update bwrap info: {key}")
 
 
-def prepare_bwrap(bwrap_installpath):
+def prepare_bwrap(bwrap_installpath: str) -> None:
     """
     Prepare for running EasyBuild with bwrap:
     - update _bwrap_info
diff --git a/easybuild/tools/config.py b/easybuild/tools/config.py
index d6769442d9..6ecd3ac5f3 100644
--- a/easybuild/tools/config.py
+++ b/easybuild/tools/config.py
@@ -46,6 +46,7 @@
 import time
 from abc import ABCMeta
 from string import ascii_letters
+from typing import Any, Dict, Optional
 
 from easybuild.base import fancylogger
 from easybuild.base.frozendict import FrozenDictKnownKeys
@@ -216,7 +217,7 @@ def __call__(cls, *args, **kwargs):
 
 
 # utility function for obtaining default paths
-def mk_full_default_path(name, prefix=DEFAULT_PREFIX):
+def mk_full_default_path(name: str, prefix: str = DEFAULT_PREFIX) -> str:
     """Create full path, avoid '/' at the end."""
     args = [prefix]
     path = DEFAULT_PATH_SUBDIRS[name]
@@ -581,12 +582,12 @@ class BuildOptions(BaseBuildOptions):
     KNOWN_KEYS = [k for kss in [BUILD_OPTIONS_CMDLINE, BUILD_OPTIONS_OTHER] for ks in kss.values() for k in ks]
 
 
-def get_pretend_installpath():
+def get_pretend_installpath() -> str:
     """Get the installpath when --pretend option is used"""
     return os.path.join(os.path.expanduser('~'), 'easybuildinstall')
 
 
-def init(options, config_options_dict):
+def init(options, config_options_dict: dict) -> None:
     """
     Gather all variables and check if they're valid
     Variables are read in this order of preference: generaloption > legacy environment > legacy config file
@@ -678,7 +679,7 @@ def init_build_options(build_options=None, cmdline_options=None):
     return BuildOptions(bo)
 
 
-def build_option(key, **kwargs):
+def build_option(key: str, **kwargs) -> Any:
     """Obtain value specified build option."""
 
     # return build option value if BuildOptions has been initialised and it's a known build option
@@ -699,7 +700,7 @@ def build_option(key, **kwargs):
         raise EasyBuildError(error_msg, exit_code=EasyBuildExit.OPTION_ERROR)
 
 
-def update_build_option(key, value):
+def update_build_option(key: str, value: Any) -> Any:
     """
     Update build option with specified name to given value.
 
@@ -715,7 +716,7 @@ def update_build_option(key, value):
     return orig_value
 
 
-def update_build_options(key_value_dict):
+def update_build_options(key_value_dict: Dict[str, Any]) -> Dict[str, Any]:
     """
     Update build options as specified by the given dictionary (where keys are assumed to be build option names).
     Returns dictionary with original values for the updated build options.
@@ -729,33 +730,33 @@ def update_build_options(key_value_dict):
     return orig_key_value_dict
 
 
-def build_path():
+def build_path() -> Any:
     """
     Return the build path
     """
     return ConfigurationVariables()['buildpath']
 
 
-def source_paths():
+def source_paths() -> Any:
     """
     Return the list of source paths for software
     """
     return ConfigurationVariables()['sourcepath']
 
 
-def source_paths_data():
+def source_paths_data() -> Any:
     """
     Return the list of source paths for data
     """
     return ConfigurationVariables()['sourcepath_data']
 
 
-def source_path():
+def source_path() -> None:
     """NO LONGER SUPPORTED: use source_paths instead"""
     _log.nosupport("source_path() is replaced by source_paths()", '2.0')
 
 
-def install_path(typ=None):
+def install_path(typ: Optional[str] = None) -> str:
     """
     Returns the install path
     - subdir 'software' for actual software installation (default)
@@ -788,42 +789,42 @@ def install_path(typ=None):
     return res
 
 
-def get_repository():
+def get_repository() -> Any:
     """
     Return the repository (git, svn or file)
     """
     return ConfigurationVariables()['repository']
 
 
-def get_repositorypath():
+def get_repositorypath() -> Any:
     """
     Return the repository path
     """
     return ConfigurationVariables()['repositorypath']
 
 
-def get_package_naming_scheme():
+def get_package_naming_scheme() -> Any:
     """
     Return the package naming scheme
     """
     return ConfigurationVariables()['package_naming_scheme']
 
 
-def package_path():
+def package_path() -> Any:
     """
     Return the path where built packages are copied to
     """
     return ConfigurationVariables()['packagepath']
 
 
-def container_path():
+def container_path() -> Any:
     """
     Return the path for container recipes & images
     """
     return ConfigurationVariables()['containerpath']
 
 
-def get_modules_tool():
+def get_modules_tool() -> Optional[Any]:
     """
     Return modules tool (EnvironmentModules, Lmod, ...)
     """
@@ -831,14 +832,14 @@ def get_modules_tool():
     return ConfigurationVariables().get('modules_tool', None)
 
 
-def get_module_naming_scheme():
+def get_module_naming_scheme() -> Any:
     """
     Return module naming scheme (EasyBuildMNS, HierarchicalMNS, ...)
     """
     return ConfigurationVariables()['module_naming_scheme']
 
 
-def get_job_backend():
+def get_job_backend() -> Optional[Any]:
     """
     Return job execution backend (PBS, GC3Pie, ...)
     """
@@ -846,14 +847,14 @@ def get_job_backend():
     return ConfigurationVariables().get('job_backend', None)
 
 
-def get_module_syntax():
+def get_module_syntax() -> Any:
     """
     Return module syntax (Lua, Tcl)
     """
     return ConfigurationVariables()['module_syntax']
 
 
-def get_output_style():
+def get_output_style() -> str:
     """Return output style to use."""
 
     output_style = build_option('output_style', default=OUTPUT_STYLE_BASIC)
@@ -873,7 +874,8 @@ def get_output_style():
     return output_style
 
 
-def log_file_format(return_directory=False, ec=None, date=None, timestamp=None):
+def log_file_format(return_directory: bool = False, ec: Optional[Dict[str, Any]] = None,
+                    date: Optional[str] = None, timestamp: Optional[str] = None) -> str:
     """
     Return the format for the logfile or the directory
 
@@ -909,7 +911,7 @@ def log_file_format(return_directory=False, ec=None, date=None, timestamp=None):
     return res
 
 
-def log_format(ec=None):
+def log_format(ec: Optional[Dict[str, Any]] = None) -> str:
     """
     Return the logfilename format
     """
@@ -917,7 +919,7 @@ def log_format(ec=None):
     return log_file_format(return_directory=False, ec=ec)
 
 
-def log_path(ec=None):
+def log_path(ec: Optional[Dict[str, Any]] = None) -> str:
     """
     Return the log path
     """
@@ -926,7 +928,7 @@ def log_path(ec=None):
     return log_file_format(return_directory=True, ec=ec, date=date, timestamp=timestamp)
 
 
-def get_failed_install_build_dirs_path(ec):
+def get_failed_install_build_dirs_path(ec: Dict[str, Any]) -> Optional[str]:
     """
     Return the location where the build directory is copied to if installation failed
 
@@ -944,7 +946,7 @@ def get_failed_install_build_dirs_path(ec):
     return os.path.join(base_path, f'{name}-{version}')
 
 
-def get_failed_install_logs_path(ec):
+def get_failed_install_logs_path(ec: Dict[str, Any]) -> Optional[str]:
     """
     Return the location where log files are copied to if installation failed
 
@@ -962,7 +964,7 @@ def get_failed_install_logs_path(ec):
     return os.path.join(base_path, f'{name}-{version}')
 
 
-def get_build_log_path():
+def get_build_log_path() -> str:
     """
     Return (temporary) directory for build log
     """
@@ -974,7 +976,8 @@ def get_build_log_path():
     return res
 
 
-def get_log_filename(name, version, add_salt=False, date=None, timestamp=None):
+def get_log_filename(name: str, version: str, add_salt: bool = False, date: Optional[str] = None,
+                     timestamp: Optional[str] = None) -> str:
     """
     Generate a filename to be used for logging
 
@@ -1008,7 +1011,7 @@ def get_log_filename(name, version, add_salt=False, date=None, timestamp=None):
     return filepath
 
 
-def find_last_log(curlog):
+def find_last_log(curlog: str) -> Optional[str]:
     """
     Find location to last log file that is still available.
 
@@ -1058,13 +1061,13 @@ def find_last_log(curlog):
     return res
 
 
-def module_classes():
+def module_classes() -> Any:
     """
     Return list of module classes specified in config file.
     """
     return ConfigurationVariables()['moduleclasses']
 
 
-def read_environment(env_vars, strict=False):
+def read_environment(env_vars, strict: bool = False) -> None:
     """NO LONGER SUPPORTED: use read_environment from easybuild.tools.environment instead"""
     _log.nosupport("read_environment has moved to easybuild.tools.environment", '2.0')
diff --git a/easybuild/tools/entrypoints.py b/easybuild/tools/entrypoints.py
index 1f7702d295..7d074eb6ce 100644
--- a/easybuild/tools/entrypoints.py
+++ b/easybuild/tools/entrypoints.py
@@ -30,11 +30,12 @@
 """
 import sys
 import importlib
+from typing import Any, ClassVar, Dict, List, Optional, Set, TypeVar
+
 from easybuild.tools.config import build_option
 
 from easybuild.base import fancylogger
 from easybuild.tools.build_log import EasyBuildError
-from typing import TypeVar, List, Set, Any
 
 _T = TypeVar('_T')
 
@@ -56,9 +57,9 @@
 
 
 class EasybuildEntrypoint:
-    group = None
+    group: Optional[str] = None  # Subclasses MUST override this
     expected_type = None
-    registered = {}
+    registered: ClassVar[Dict[str, Set["EasybuildEntrypoint"]]] = {}
 
     def __init__(self):
         if self.group is None:
diff --git a/easybuild/tools/environment.py b/easybuild/tools/environment.py
index 86e79c9830..e47136cfc3 100644
--- a/easybuild/tools/environment.py
+++ b/easybuild/tools/environment.py
@@ -32,6 +32,7 @@
 """
 import copy
 import os
+from typing import Dict
 
 from easybuild.base import fancylogger
 from easybuild.tools.build_log import EasyBuildError, dry_run_msg
@@ -45,7 +46,7 @@
 
 _log = fancylogger.getLogger('environment', fname=False)
 
-_changes = {}
+_changes: Dict[str, str] = {}
 
 
 def write_changes(filename):
diff --git a/easybuild/tools/filetools.py b/easybuild/tools/filetools.py
index 366f7b87fc..19c8b78c4e 100644
--- a/easybuild/tools/filetools.py
+++ b/easybuild/tools/filetools.py
@@ -60,6 +60,7 @@
 import time
 import zlib
 from functools import partial
+from typing import Any, IO, List, Optional, Sequence, Union
 from html.parser import HTMLParser
 import urllib.request as std_urllib
 
@@ -194,7 +195,7 @@ class ZlibChecksum:
     match the interface of the hashlib module
     """
 
-    def __init__(self, algorithm):
+    def __init__(self, algorithm) -> None:
         self.algorithm = algorithm
         self.checksum = algorithm(b'')  # use the same starting point as the module
         self.blocksize = 64  # The same as md5/sha1
@@ -208,7 +209,7 @@ def hexdigest(self):
         return '0x%s' % (self.checksum & 0xffffffff)
 
 
-def is_readable(path):
+def is_readable(path: str) -> bool:
     """Return whether file at specified location exists and is readable."""
     try:
         return os.path.exists(path) and os.access(path, os.R_OK)
@@ -216,7 +217,7 @@ def is_readable(path):
         raise EasyBuildError("Failed to check whether %s is readable: %s", path, err)
 
 
-def open_file(path, mode):
+def open_file(path: str, mode: str) -> IO[Any]:
     """Open a (usually) text file. If mode is not binary, then utf-8 encoding will be used"""
     # This is required for text files in Python 3, especially until Python 3.7 which implements PEP 540.
     # This PEP opens files in UTF-8 mode if the C locale is used, see https://www.python.org/dev/peps/pep-0540
@@ -226,7 +227,7 @@ def open_file(path, mode):
         return open(path, mode)
 
 
-def read_file(path, log_error=True, mode='r'):
+def read_file(path: str, log_error: bool = True, mode: str = 'r') -> Optional[Union[str, bytes]]:
     """Read contents of file at given path, in a robust way."""
     txt = None
     try:
@@ -239,8 +240,9 @@ def read_file(path, log_error=True, mode='r'):
     return txt
 
 
-def write_file(path, data, append=False, forced=False, backup=False, always_overwrite=True, verbose=False,
-               show_progress=False, size=None):
+def write_file(path: str, data, append: bool = False, forced: bool = False, backup: bool = False,
+               always_overwrite: bool = True, verbose: bool = False, show_progress: bool = False,
+               size: Optional[int] = None) -> None:
     """
     Write given contents to file at given path;
     overwrites current file contents without backup by default!
@@ -311,14 +313,14 @@ def write_file(path, data, append=False, forced=False, backup=False, always_over
         raise EasyBuildError("Failed to write to %s: %s", path, err)
 
 
-def is_binary(contents):
+def is_binary(contents) -> bool:
     """
     Check whether given bytestring represents the contents of a binary file or not.
     """
     return isinstance(contents, bytes) and b'\00' in bytes(contents)
 
 
-def resolve_path(path):
+def resolve_path(path: str) -> str:
     """
     Return fully resolved path for given path.
 
@@ -332,7 +334,7 @@ def resolve_path(path):
     return resolved_path
 
 
-def symlink(source_path, symlink_path, use_abspath_source=True):
+def symlink(source_path: str, symlink_path: str, use_abspath_source: bool = True) -> None:
     """
     Create a symlink at the specified path to the given path.
 
@@ -358,7 +360,7 @@ def symlink(source_path, symlink_path, use_abspath_source=True):
             raise EasyBuildError("Symlinking %s to %s failed: %s", source_path, symlink_path, err)
 
 
-def remove_file(path):
+def remove_file(path: str) -> None:
     """Remove file at specified path."""
 
     # early exit in 'dry run' mode
@@ -374,7 +376,7 @@ def remove_file(path):
         raise EasyBuildError("Failed to remove file %s: %s", path, err)
 
 
-def empty_dir(path):
+def empty_dir(path: str) -> None:
     """Empty directory at specified path, keeping directory itself intact."""
     # early exit in 'dry run' mode
     if build_option('extended_dry_run'):
@@ -394,7 +396,7 @@ def empty_dir(path):
             raise EasyBuildError(f"Failed to empty directory {path}: {err}")
 
 
-def remove_dir(path):
+def remove_dir(path: str) -> None:
     """Remove directory at specified path."""
     # early exit in 'dry run' mode
     if build_option('extended_dry_run'):
@@ -436,7 +438,7 @@ def clean_dir(path):
         empty_dir(path)
 
 
-def remove(paths):
+def remove(paths: Union[str, Sequence[str]]) -> None:
     """
     Remove single file/directory or list of files and directories
 
@@ -456,7 +458,7 @@ def remove(paths):
             raise EasyBuildError("Specified path to remove is not an existing file or directory: %s", path)
 
 
-def get_cwd(must_exist=True):
+def get_cwd(must_exist: bool = True) -> Optional[str]:
     """
     Retrieve current working directory
     """
@@ -472,7 +474,7 @@ def get_cwd(must_exist=True):
     return cwd
 
 
-def change_dir(path):
+def change_dir(path: str) -> Optional[str]:
     """
     Change to directory at specified location.
 
@@ -494,8 +496,9 @@ def change_dir(path):
     return prev_dir
 
 
-def extract_file(fn, dest, cmd=None, extra_options=None, overwrite=False, forced=False, change_into_dir=False,
-                 trace=True):
+def extract_file(fn: str, dest: str, cmd: Optional[str] = None, extra_options: Optional[str] = None,
+                 overwrite: bool = False, forced: bool = False, change_into_dir: bool = False,
+                 trace: bool = True) -> str:
     """
     Extract file at given path to specified directory
     :param fn: path to file to extract
@@ -551,7 +554,7 @@ def extract_file(fn, dest, cmd=None, extra_options=None, overwrite=False, forced
     return base_dir
 
 
-def which(cmd, retain_all=False, check_perms=True, log_ok=True, on_error=WARN):
+def which(cmd: str, retain_all: bool = False, check_perms: bool = True, log_ok: bool = True, on_error=WARN):
     """
     Return (first) path in $PATH for specified command, or None if command is not found
 
@@ -564,7 +567,7 @@ def which(cmd, retain_all=False, check_perms=True, log_ok=True, on_error=WARN):
         raise EasyBuildError("Invalid value for 'on_error': %s", on_error)
 
     if retain_all:
-        res = []
+        res: List[str] = []
     else:
         res = None
 
@@ -595,7 +598,7 @@ def which(cmd, retain_all=False, check_perms=True, log_ok=True, on_error=WARN):
     return res
 
 
-def det_common_path_prefix(paths):
+def det_common_path_prefix(paths: List[str]) -> Optional[str]:
     """Determine common path prefix for a given list of paths."""
     if not isinstance(paths, list):
         raise EasyBuildError("det_common_path_prefix: argument must be of type list (got %s: %s)", type(paths), paths)
diff --git a/easybuild/tools/hooks.py b/easybuild/tools/hooks.py
index 55bfa9087b..c1725a1662 100644
--- a/easybuild/tools/hooks.py
+++ b/easybuild/tools/hooks.py
@@ -31,13 +31,14 @@
 """
 import difflib
 import os
+from typing import Any, Dict, Callable
+from importlib.util import spec_from_file_location, module_from_spec
 
 from easybuild.tools.entrypoints import EntrypointHook
 
 from easybuild.base import fancylogger
 from easybuild.tools.build_log import EasyBuildError, print_msg
 from easybuild.tools.config import build_option
-from importlib.util import spec_from_file_location, module_from_spec
 
 
 _log = fancylogger.getLogger('hooks', fname=False)
@@ -122,7 +123,7 @@
 
 
 # cached version of hooks, to avoid having to load them from file multiple times
-_cached_hooks = {}
+_cached_hooks: Dict[str, Dict[str, Callable[..., Any]]] = {}
 
 
 def load_source(filename, path):
diff --git a/easybuild/tools/include.py b/easybuild/tools/include.py
index 9c026647df..3cda193256 100644
--- a/easybuild/tools/include.py
+++ b/easybuild/tools/include.py
@@ -34,6 +34,7 @@
 import re
 import sys
 import tempfile
+from typing import Optional, Sequence
 
 from easybuild.base import fancylogger
 from easybuild.tools.build_log import EasyBuildError
@@ -82,7 +83,7 @@
 """
 
 
-def create_pkg(path, pkg_init_body=None):
+def create_pkg(path: str, pkg_init_body: Optional[str] = None) -> None:
     """Write package __init__.py file at specified path."""
     init_path = os.path.join(path, '__init__.py')
     try:
@@ -102,7 +103,8 @@ def create_pkg(path, pkg_init_body=None):
         raise EasyBuildError("Failed to create package at %s: %s", path, err)
 
 
-def set_up_eb_package(parent_path, eb_pkg_name, subpkgs=None, pkg_init_body=None):
+def set_up_eb_package(parent_path: str, eb_pkg_name: str, subpkgs: Optional[Sequence[str]] = None,
+                      pkg_init_body: Optional[str] = None) -> None:
     """
     Set up new easybuild subnamespace in specified path.
 
@@ -127,7 +129,7 @@ def set_up_eb_package(parent_path, eb_pkg_name, subpkgs=None, pkg_init_body=None
         pkgpath = os.path.dirname(pkgpath)
 
 
-def verify_imports(pymods, pypkg, from_path):
+def verify_imports(pymods: Sequence[str], pypkg: str, from_path: str) -> None:
     """Verify that import of specified modules from specified package and expected location works."""
 
     pymod_specs = ['%s.%s' % (pypkg, pymod) for pymod in pymods]
@@ -155,13 +157,13 @@ def verify_imports(pymods, pypkg, from_path):
         _log.debug("Import of %s from %s verified", pymod_spec, from_path)
 
 
-def is_software_specific_easyblock(module):
+def is_software_specific_easyblock(module: str) -> bool:
     """Determine whether Python module at specified location is a software-specific easyblock."""
     # All software-specific easyblocks start with the prefix and derive from another class, at least EasyBlock
     return bool(re.search(r"^class %s[^(:]+\([^)]+\):\s*$" % EASYBLOCK_CLASS_PREFIX, read_file(module), re.M))
 
 
-def include_easyblocks(tmpdir, paths):
+def include_easyblocks(tmpdir: str, paths: Sequence[str]) -> str:
     """Include generic and software-specific easyblocks found in specified locations."""
     easyblocks_path = tempfile.mkdtemp(dir=tmpdir, prefix='included-easyblocks-')
 
@@ -211,7 +213,7 @@ def include_easyblocks(tmpdir, paths):
     return easyblocks_path
 
 
-def include_module_naming_schemes(tmpdir, paths):
+def include_module_naming_schemes(tmpdir: str, paths: Sequence[str]) -> str:
     """Include module naming schemes at specified locations."""
     mns_path = os.path.join(tmpdir, 'included-module-naming-schemes')
 
@@ -243,7 +245,7 @@ def include_module_naming_schemes(tmpdir, paths):
     return mns_path
 
 
-def include_toolchains(tmpdir, paths):
+def include_toolchains(tmpdir: str, paths: Sequence[str]) -> str:
     """Include toolchains and toolchain components at specified locations."""
     toolchains_path = os.path.join(tmpdir, 'included-toolchains')
     toolchain_subpkgs = ['compiler', 'fft', 'linalg', 'mpi']
diff --git a/easybuild/tools/jenkins.py b/easybuild/tools/jenkins.py
index f823be518c..11501877e1 100644
--- a/easybuild/tools/jenkins.py
+++ b/easybuild/tools/jenkins.py
@@ -34,6 +34,7 @@
 import xml.dom.minidom as xml
 
 from datetime import datetime
+from typing import Any, Dict, Sequence, Tuple
 
 from easybuild.base import fancylogger
 from easybuild.tools.build_log import EasyBuildError
@@ -43,7 +44,8 @@
 _log = fancylogger.getLogger('jenkins', fname=False)
 
 
-def write_to_xml(succes, failed, filename):
+def write_to_xml(succes: Sequence[Tuple[Any, Dict[str, Any]]],
+                 failed: Sequence[Tuple[Any, str, str, Any]], filename: str) -> None:
     """
     Create xml output, using minimal output required according to
     http://stackoverflow.com/questions/4922867/junit-xml-format-specification-that-hudson-supports
@@ -113,7 +115,7 @@ def create_success(name, stats):
         raise EasyBuildError("Failed to write out XML file %s: %s", filename, err)
 
 
-def aggregate_xml_in_dirs(base_dir, output_filename):
+def aggregate_xml_in_dirs(base_dir: str, output_filename: str) -> None:
     """
     Finds all the xml files in the dirs and takes the testcase attribute out of them.
     These are then put in a single output file.
diff --git a/easybuild/tools/job/backend.py b/easybuild/tools/job/backend.py
index b3e43d777d..f2ee487b6b 100644
--- a/easybuild/tools/job/backend.py
+++ b/easybuild/tools/job/backend.py
@@ -33,6 +33,7 @@
 
 from abc import ABCMeta, abstractmethod
 from types import SimpleNamespace
+from typing import Any, Optional
 
 from easybuild.base import fancylogger
 from easybuild.tools.config import get_job_backend
@@ -50,7 +51,7 @@ def __init__(self):
     @abstractmethod
     def _check_version(self):
         """Check whether version of backend complies with required version."""
-        pass
+        return None
 
     @abstractmethod
     def init(self):
@@ -60,10 +61,11 @@ def init(self):
         Jobs may be queued and only actually submitted when `complete()`
         is called.
         """
-        pass
+        return None
 
     @abstractmethod
-    def make_job(self, script, name, env_vars=None, hours=None, cores=None):
+    def make_job(self, script: str, name: str, env_vars: Optional[dict] = None,
+                 hours: Optional[int] = None, cores: Optional[int] = None) -> Any:
         """
         Create and return a `Job` object with the given parameters.
 
@@ -84,7 +86,7 @@ def queue(self, job, dependencies=frozenset()):
         Note that actual submission may be delayed until `complete()` is
         called.
         """
-        pass
+        return None
 
     @abstractmethod
     def complete(self):
@@ -97,7 +99,7 @@ def complete(self):
         No more job submissions should be attempted after `complete()`
         has been called, until a `init()` is invoked again.
         """
-        pass
+        return None
 
 
 def avail_job_backends(check_usable=True):
diff --git a/easybuild/tools/loose_version.py b/easybuild/tools/loose_version.py
index af74d5167c..18579a54fd 100644
--- a/easybuild/tools/loose_version.py
+++ b/easybuild/tools/loose_version.py
@@ -15,6 +15,9 @@
 from itertools import zip_longest
 
 
+from typing import Iterable, Optional, Union
+
+
 class LooseVersion:
     """Version numbering for anarchists and software realists.
 
@@ -26,7 +29,7 @@ class LooseVersion:
 
     component_re = re.compile(r'(\d+ | [a-z]+ | \.)', re.VERBOSE)
 
-    def __init__(self, vstring=None):
+    def __init__(self, vstring: Optional[str] = None) -> None:
         self._vstring = vstring
         if vstring:
             components = [x for x in self.component_re.split(vstring)
@@ -50,7 +53,7 @@ def version(self):
         """Readonly access to the parsed version (list or None)"""
         return self._version
 
-    def is_prerelease(self, other, markers):
+    def is_prerelease(self, other: Union[str, 'LooseVersion'], markers: Iterable[str]) -> bool:
         """Check if this is a prerelease of other
 
         Markers is a list of strings that denote a prerelease
@@ -66,13 +69,13 @@ def is_prerelease(self, other, markers):
                     return True
         return False
 
-    def __str__(self):
+    def __str__(self) -> str:
         return self._vstring
 
-    def __repr__(self):
+    def __repr__(self) -> str:
         return "LooseVersion ('%s')" % str(self)
 
-    def _cmp(self, other):
+    def _cmp(self, other: Union[str, 'LooseVersion']) -> int:
         """Rich comparison method used by the operators below"""
         if isinstance(other, str):
             other = LooseVersion(other)
@@ -93,20 +96,20 @@ def _cmp(self, other):
                 return 1
         return 0
 
-    def __eq__(self, other):
+    def __eq__(self, other: object) -> bool:
         return self._cmp(other) == 0
 
-    def __ne__(self, other):
+    def __ne__(self, other: object) -> bool:
         return self._cmp(other) != 0
 
-    def __lt__(self, other):
+    def __lt__(self, other: object) -> bool:
         return self._cmp(other) < 0
 
-    def __le__(self, other):
+    def __le__(self, other: object) -> bool:
         return self._cmp(other) <= 0
 
-    def __gt__(self, other):
+    def __gt__(self, other: object) -> bool:
         return self._cmp(other) > 0
 
-    def __ge__(self, other):
+    def __ge__(self, other: object) -> bool:
         return self._cmp(other) >= 0
diff --git a/easybuild/tools/module_generator.py b/easybuild/tools/module_generator.py
index bba73f8684..db66b89c57 100644
--- a/easybuild/tools/module_generator.py
+++ b/easybuild/tools/module_generator.py
@@ -44,6 +44,7 @@
 from contextlib import contextmanager
 from string import Template
 from textwrap import wrap
+from typing import List
 
 from easybuild.base import fancylogger
 from easybuild.tools import LooseVersion
@@ -1224,7 +1225,7 @@ class ModuleGeneratorLua(ModuleGenerator):
     SYNTAX = 'Lua'
     MODULE_FILE_EXTENSION = '.lua'
     MODULE_SHEBANG = ''  # no 'shebang' in Lua module files
-    CHARS_TO_ESCAPE = []
+    CHARS_TO_ESCAPE: List[str] = []
 
     INSTALLDIR_REGEX = r'^local root\s+=\s+"(?P<installdir>.*)"'
     LOAD_REGEX = r'^\s*(?:load|depends_on)\("(\S+)"'
diff --git a/easybuild/tools/module_naming_scheme/toolchain.py b/easybuild/tools/module_naming_scheme/toolchain.py
index 7e9e59295f..d3fcfe95db 100644
--- a/easybuild/tools/module_naming_scheme/toolchain.py
+++ b/easybuild/tools/module_naming_scheme/toolchain.py
@@ -30,6 +30,7 @@
 * Kenneth Hoste (Ghent University)
 """
 import copy
+from typing import Any, Dict, Tuple
 
 from easybuild.base import fancylogger
 from easybuild.framework.easyconfig.easyconfig import EasyConfig, process_easyconfig, robot_find_easyconfig
@@ -39,7 +40,7 @@
 
 _log = fancylogger.getLogger('module_naming_scheme.toolchain', fname=False)
 
-_toolchain_details_cache = {}
+_toolchain_details_cache: Dict[Tuple[str, str, str], Any] = {}
 
 
 # different types of toolchain elements
diff --git a/easybuild/tools/modules.py b/easybuild/tools/modules.py
index 41a4174650..2026595705 100644
--- a/easybuild/tools/modules.py
+++ b/easybuild/tools/modules.py
@@ -42,6 +42,7 @@
 import re
 import shlex
 from enum import Enum
+from typing import Any, Dict, Optional, Tuple, Type
 
 from easybuild.base import fancylogger
 from easybuild.tools import LooseVersion
@@ -123,14 +124,14 @@
 }
 # cache for result of module subcommands
 # key: tuple with $MODULEPATH and (stringified) list of extra arguments/options for module subcommand
-# value: result of module subcommand
-MODULE_AVAIL_CACHE = {}
-MODULE_SHOW_CACHE = {}
+# value: result of module subcommand (various types)
+MODULE_AVAIL_CACHE: Dict[Tuple[str, str], Any] = {}
+MODULE_SHOW_CACHE: Dict[Tuple[str, str], Any] = {}
 
 # cache for modules tool version
 # cache key: module command
 # value: corresponding (validated) module version
-MODULE_VERSION_CACHE = {}
+MODULE_VERSION_CACHE: Dict[str, str] = {}
 
 
 _log = fancylogger.getLogger('modules', fname=False)
@@ -568,30 +569,30 @@ def set_alias_vars(self, alias, value):
 class ModulesTool:
     """An abstract interface to a tool that deals with modules."""
     # name of this modules tool (used in log/warning/error messages)
-    NAME = None
+    NAME: Optional[str] = None
     # position and optionname
     TERSE_OPTION = (0, '--terse')
     # module command to use
-    COMMAND = None
+    COMMAND: Optional[str] = None
     # environment variable to determine path to module command;
     # used as fallback in case command is not available in $PATH
-    COMMAND_ENVIRONMENT = None
+    COMMAND_ENVIRONMENT: Optional[str] = None
     # run module command explicitly using this shell
     COMMAND_SHELL = None
     # option to determine the version
     VERSION_OPTION = '--version'
     # minimal required version (cannot include -beta or rc)
-    REQ_VERSION = None
+    REQ_VERSION: Optional[str] = None
     # minimal required version to check user's group in modulefile
-    REQ_VERSION_TCL_CHECK_GROUP = None
+    REQ_VERSION_TCL_CHECK_GROUP: Optional[str] = None
     # deprecated version limit (support for versions below this version is deprecated)
-    DEPR_VERSION = None
+    DEPR_VERSION: Optional[str] = None
     # maximum version allowed (cannot include -beta or rc)
-    MAX_VERSION = None
+    MAX_VERSION: Optional[str] = None
     # the regexp, should have a "version" group (multiline search)
-    VERSION_REGEXP = None
+    VERSION_REGEXP: Optional[str] = None
     # modules tool user cache directory
-    USER_CACHE_DIR = None
+    USER_CACHE_DIR: Optional[str] = None
 
     def __init__(self, mod_paths=None, testing=False):
         """
@@ -2266,7 +2267,7 @@ def mk_module_path(paths):
     return ':'.join(paths)
 
 
-def avail_modules_tools():
+def avail_modules_tools() -> Dict[str, Type['ModulesTool']]:
     """
     Return all known modules tools.
     """
diff --git a/easybuild/tools/options.py b/easybuild/tools/options.py
index b602af7a91..53a0e50fde 100644
--- a/easybuild/tools/options.py
+++ b/easybuild/tools/options.py
@@ -46,6 +46,7 @@
 import tempfile
 import pwd
 from collections import OrderedDict
+from typing import Any, Dict, Tuple
 
 import easybuild.tools.environment as env
 from easybuild.base import fancylogger  # build_log should always stay there, to ensure EasyBuildLog
@@ -157,7 +158,7 @@ def cleanup_and_exit(tmpdir):
     sys.exit(0)
 
 
-def pretty_print_opts(opts_dict):
+def pretty_print_opts(opts_dict: Dict[str, Tuple[Any, Any]]) -> None:
     """
     Pretty print options dict.
 
@@ -194,7 +195,7 @@ def pretty_print_opts(opts_dict):
     print('\n'.join(lines))
 
 
-def use_color(colorize, stream=sys.stdout):
+def use_color(colorize, stream: Any = sys.stdout) -> bool:
     """
     Return ``True`` or ``False`` depending on whether ANSI color
     escapes are to be used when printing to `stream`.
diff --git a/easybuild/tools/output.py b/easybuild/tools/output.py
index d1cf1810be..58a443d830 100644
--- a/easybuild/tools/output.py
+++ b/easybuild/tools/output.py
@@ -35,6 +35,8 @@
 from collections import OrderedDict
 import sys
 
+from typing import Any, Dict, Optional
+
 from easybuild.tools.build_log import EasyBuildError
 from easybuild.tools.config import OUTPUT_STYLE_RICH, build_option, get_output_style
 
@@ -76,7 +78,7 @@
 _progress_bar_cache = {}
 
 
-def colorize(txt, color):
+def colorize(txt: str, color: str) -> str:
     """
     Colorize given text, with specified color.
     """
@@ -91,7 +93,7 @@ def colorize(txt, color):
     return coltxt
 
 
-def escape_for_rich(txt):
+def escape_for_rich(txt: str) -> str:
     """Make sure the text can be printed with rich if that is used"""
     if use_rich():
         txt = rich.markup.escape(txt)
@@ -105,42 +107,42 @@ class DummyRich:
     """
 
     # __enter__ and __exit__ must be implemented to allow use as context manager
-    def __enter__(self, *args, **kwargs):
+    def __enter__(self, *args, **kwargs) -> None:
         pass
 
-    def __exit__(self, *args, **kwargs):
+    def __exit__(self, *args, **kwargs) -> None:
         pass
 
     # dummy implementations for methods supported by rich.progress.Progress class
-    def add_task(self, *args, **kwargs):
+    def add_task(self, *args, **kwargs) -> None:
         pass
 
-    def stop_task(self, *args, **kwargs):
+    def stop_task(self, *args, **kwargs) -> None:
         pass
 
-    def update(self, *args, **kwargs):
+    def update(self, *args, **kwargs) -> None:
         pass
 
     # internal Rich methods
-    def __rich_console__(self, *args, **kwargs):
+    def __rich_console__(self, *args, **kwargs) -> None:
         pass
 
 
-def use_rich():
+def use_rich() -> bool:
     """
     Return whether or not to use Rich to produce rich output.
     """
     return get_output_style() == OUTPUT_STYLE_RICH
 
 
-def show_progress_bars():
+def show_progress_bars() -> bool:
     """
     Return whether or not to show progress bars.
     """
     return use_rich() and build_option('show_progress_bar') and not build_option('extended_dry_run')
 
 
-def rich_live_cm():
+def rich_live_cm() -> object:
     """
     Return Live instance to use as context manager.
     """
@@ -165,7 +167,7 @@ def progress_bar_cache(func):
     Function decorator to cache created progress bars for easy retrieval.
     """
     @functools.wraps(func)
-    def new_func(ignore_cache=False):
+    def new_func(ignore_cache: bool = False) -> object:
         if hasattr(func, 'cached') and not ignore_cache:
             progress_bar = func.cached
         elif use_rich() and build_option('show_progress_bar'):
@@ -180,7 +182,7 @@ def new_func(ignore_cache=False):
 
 
 @progress_bar_cache
-def status_bar():
+def status_bar() -> object:
     """
     Get progress bar to display overall progress.
     """
@@ -193,7 +195,7 @@ def status_bar():
 
 
 @progress_bar_cache
-def easyconfig_progress_bar():
+def easyconfig_progress_bar() -> object:
     """
     Get progress bar to display progress for installing a single easyconfig file.
     """
@@ -209,7 +211,7 @@ def easyconfig_progress_bar():
 
 
 @progress_bar_cache
-def download_all_progress_bar():
+def download_all_progress_bar() -> object:
     """
     Get progress bar to show progress on downloading of all source files.
     """
@@ -224,7 +226,7 @@ def download_all_progress_bar():
 
 
 @progress_bar_cache
-def download_one_progress_bar():
+def download_one_progress_bar() -> object:
     """
     Get progress bar to show progress for downloading a file of known size.
     """
@@ -240,7 +242,7 @@ def download_one_progress_bar():
 
 
 @progress_bar_cache
-def download_one_progress_bar_unknown_size():
+def download_one_progress_bar_unknown_size() -> object:
     """
     Get progress bar to show progress for downloading a file of unknown size.
     """
@@ -254,7 +256,7 @@ def download_one_progress_bar_unknown_size():
 
 
 @progress_bar_cache
-def extensions_progress_bar():
+def extensions_progress_bar() -> object:
     """
     Get progress bar to show progress for installing extensions.
     """
@@ -267,7 +269,7 @@ def extensions_progress_bar():
     return progress_bar
 
 
-def get_progress_bar(bar_type, ignore_cache=False, size=None):
+def get_progress_bar(bar_type: str, ignore_cache: bool = False, size: Optional[int] = None) -> object:
     """
     Get progress bar of given type.
     """
@@ -282,7 +284,7 @@ def get_progress_bar(bar_type, ignore_cache=False, size=None):
     return pbar
 
 
-def start_progress_bar(bar_type, size, label=None):
+def start_progress_bar(bar_type: str, size: Optional[int], label: Optional[str] = None) -> None:
     """
     Start progress bar of given type.
 
@@ -303,7 +305,8 @@ def start_progress_bar(bar_type, size, label=None):
         pbar.update(task_id, description=label)
 
 
-def update_progress_bar(bar_type, label=None, progress_size=1, total=None):
+def update_progress_bar(bar_type: str, label: Optional[str] = None, progress_size: int = 1,
+                        total: Optional[int] = None) -> None:
     """
     Update progress bar of given type (if it was started), add progress of given size.
 
@@ -321,7 +324,7 @@ def update_progress_bar(bar_type, label=None, progress_size=1, total=None):
             pbar.update(task_id, total=total)
 
 
-def stop_progress_bar(bar_type, visible=False):
+def stop_progress_bar(bar_type: str, visible: bool = False) -> None:
     """
     Stop progress bar of given type.
     """
@@ -334,7 +337,7 @@ def stop_progress_bar(bar_type, visible=False):
         raise EasyBuildError("Failed to stop %s progress bar, since it was never started?!", bar_type)
 
 
-def print_checks(checks_data):
+def print_checks(checks_data: Dict[str, Any]) -> None:
     """Print overview of checks that were made."""
 
     col_titles = checks_data.pop('col_titles', ('name', 'info', 'description'))
diff --git a/easybuild/tools/parallelbuild.py b/easybuild/tools/parallelbuild.py
index 9363ac7505..bd523e9a09 100644
--- a/easybuild/tools/parallelbuild.py
+++ b/easybuild/tools/parallelbuild.py
@@ -38,6 +38,7 @@
 import math
 import os
 import re
+from typing import Any, Dict, List, Optional, Sequence, Union
 
 from easybuild.base import fancylogger
 from easybuild.framework.easyblock import get_easyblock_instance
@@ -59,8 +60,10 @@ def _to_key(dep):
     return ActiveMNS().det_full_module_name(dep)
 
 
-def build_easyconfigs_in_parallel(build_command, easyconfigs, output_dir='easybuild-build', testing=False,
-                                  prepare_first=True, tweak_map=None, try_opts=''):
+def build_easyconfigs_in_parallel(build_command: str, easyconfigs: Sequence[Dict[str, Any]],
+                                  output_dir: str = 'easybuild-build', testing: bool = False,
+                                  prepare_first: bool = True, tweak_map: Optional[Dict[str, str]] = None,
+                                  try_opts: str = '') -> Union[str, List[Any]]:
     """
     Build easyconfigs in parallel by submitting jobs to a batch-queuing system.
     Return list of jobs submitted.
@@ -93,7 +96,7 @@ def build_easyconfigs_in_parallel(build_command, easyconfigs, output_dir='easybu
     jobs = []
 
     # keep track of which job builds which module
-    module_to_job = {}
+    module_to_job: Dict[str, Any] = {}
 
     for easyconfig in easyconfigs:
         # this is very important, otherwise we might have race conditions
@@ -183,7 +186,8 @@ def submit_jobs(ordered_ecs, cmd_line_opts, testing=False, prepare_first=True, t
                                          tweak_map=tweak_map, try_opts=try_opts_str)
 
 
-def create_job(job_backend, build_command, easyconfig, output_dir='easybuild-build', spec=''):
+def create_job(job_backend: Any, build_command: str, easyconfig: dict,
+               output_dir: str = 'easybuild-build', spec: str = '') -> Any:
     """
     Creates a job to build a *single* easyconfig.
 
@@ -228,7 +232,7 @@ def create_job(job_backend, build_command, easyconfig, output_dir='easybuild-bui
     return job
 
 
-def prepare_easyconfig(ec):
+def prepare_easyconfig(ec: Any) -> None:
     """
     Prepare for building specified easyconfig (fetch sources)
     :param ec: parsed easyconfig (EasyConfig instance)
diff --git a/easybuild/tools/robot.py b/easybuild/tools/robot.py
index ab744d32f5..4e6d312259 100644
--- a/easybuild/tools/robot.py
+++ b/easybuild/tools/robot.py
@@ -38,6 +38,7 @@
 import copy
 import os
 import sys
+from typing import Any, List, Optional, Sequence, Tuple
 
 from easybuild.base import fancylogger
 from easybuild.framework.easyconfig.easyconfig import EASYCONFIGS_ARCHIVE_DIR, ActiveMNS, process_easyconfig
@@ -54,9 +55,10 @@
 _log = fancylogger.getLogger('tools.robot', fname=False)
 
 
-def det_robot_path(robot_paths_option, tweaked_ecs_paths, extra_ec_paths, auto_robot=False):
+def det_robot_path(robot_paths_option: Sequence[str], tweaked_ecs_paths: Optional[Tuple[str, str]],
+                   extra_ec_paths: Optional[Sequence[str]], auto_robot: bool = False) -> List[str]:
     """Determine robot path."""
-    robot_path = robot_paths_option[:]
+    robot_path = list(robot_paths_option)
     _log.info("Using robot path(s): %s", robot_path)
 
     tweaked_ecs_path, tweaked_ecs_deps_path = None, None
@@ -77,7 +79,8 @@ def det_robot_path(robot_paths_option, tweaked_ecs_paths, extra_ec_paths, auto_r
     return robot_path
 
 
-def check_conflicts(easyconfigs, modtool, check_inter_ec_conflicts=True, return_conflicts=False):
+def check_conflicts(easyconfigs: list, modtool: Any, check_inter_ec_conflicts: bool = True,
+                    return_conflicts: bool = False) -> bool:
     """
     Check for conflicts in dependency graphs for specified easyconfigs.
 
@@ -105,7 +108,7 @@ def mk_key(spec):
 
     def mk_dep_keys(deps):
         """Create keys for given list of dependencies."""
-        res = []
+        res: List[Any] = []
         for dep in deps:
             # filter out dependencies marked as external module
             if not dep.get('external_module', False):
@@ -236,7 +239,8 @@ def check_conflict(parent, dep1, dep2):
     return res
 
 
-def dry_run(easyconfigs, modtool, short=False, return_modules_to_install=False):
+def dry_run(easyconfigs: list, modtool: Any, short: bool = False,
+            return_modules_to_install: bool = False) -> str:
     """
     Compose dry run overview for supplied easyconfigs:
     * [ ] for unavailable
@@ -312,7 +316,7 @@ def dry_run(easyconfigs, modtool, short=False, return_modules_to_install=False):
     return '\n'.join(lines)
 
 
-def missing_deps(easyconfigs, modtool, terse=False):
+def missing_deps(easyconfigs, modtool, terse: bool = False) -> str:
     """
     Determine subset of easyconfigs for which no module is installed yet.
     """
@@ -336,7 +340,7 @@ def missing_deps(easyconfigs, modtool, terse=False):
     return '\n'.join(lines)
 
 
-def raise_error_missing_deps(missing_deps, extra_msg=None):
+def raise_error_missing_deps(missing_deps: Sequence[Any], extra_msg: Optional[str] = None) -> None:
     """Raise error to report missing dependencies."""
 
     _log.warning("Missing dependencies (details): %s", missing_deps)
@@ -352,7 +356,8 @@ def raise_error_missing_deps(missing_deps, extra_msg=None):
     raise EasyBuildError(error_msg, exit_code=EasyBuildExit.MISSING_DEPENDENCY)
 
 
-def resolve_dependencies(easyconfigs, modtool, retain_all_deps=False, raise_error_missing_ecs=True):
+def resolve_dependencies(easyconfigs: list, modtool: Any,
+                         retain_all_deps: bool = False, raise_error_missing_ecs: bool = True) -> list:
     """
     Work through the list of easyconfigs to determine an optimal order
     :param easyconfigs: list of easyconfigs
diff --git a/easybuild/tools/run.py b/easybuild/tools/run.py
index dd081761c3..11a44a200f 100644
--- a/easybuild/tools/run.py
+++ b/easybuild/tools/run.py
@@ -48,6 +48,7 @@
 import time
 from collections import namedtuple
 from datetime import datetime
+from typing import Any, Optional, Sequence, Tuple, Union
 
 # import deprecated functions so they can still be imported from easybuild.tools.run, for now
 from easybuild._deprecated import check_async_cmd, check_log_for_errors, complete_cmd, extract_errors_from_log  # noqa
@@ -103,7 +104,7 @@
 
 class RunShellCmdError(Exception):
 
-    def __init__(self, cmd_result, caller_info, *args, **kwargs):
+    def __init__(self, cmd_result, caller_info: Tuple[str, int, str], *args, **kwargs) -> None:
         """Constructor for RunShellCmdError."""
         self.cmd = cmd_result.cmd
         self.cmd_name = os.path.basename(self.cmd.split(' ')[0])
@@ -120,7 +121,7 @@ def __init__(self, cmd_result, caller_info, *args, **kwargs):
         msg = f"Shell command '{self.cmd_name}' failed!"
         super().__init__(msg, *args, **kwargs)
 
-    def print(self):
+    def print(self) -> None:
         """
         Report failed shell command for this RunShellCmdError instance
         """
@@ -200,7 +201,7 @@ def cache_aware_func(cmd, *args, **kwargs):
     return cache_aware_func
 
 
-def fileprefix_from_cmd(cmd, allowed_chars=False):
+def fileprefix_from_cmd(cmd: str, allowed_chars: Union[bool, str] = False) -> str:
     """
     Simplify the cmd to only the allowed_chars we want in a filename
 
@@ -213,7 +214,8 @@ def fileprefix_from_cmd(cmd, allowed_chars=False):
     return ''.join([c for c in cmd if c in allowed_chars])
 
 
-def create_cmd_scripts(cmd_str, work_dir, env, tmpdir, out_file, err_file):
+def create_cmd_scripts(cmd_str: str, work_dir: str, env: Optional[dict], tmpdir: str,
+                       out_file: str, err_file: Optional[str]) -> str:
     """
     Create helper scripts for specified command in specified directory:
     - env.sh which can be sourced to define environment in which command was run;
@@ -301,7 +303,7 @@ def create_cmd_scripts(cmd_str, work_dir, env, tmpdir, out_file, err_file):
     return cmd_fp
 
 
-def _answer_question(stdout, proc, qa_patterns, qa_wait_patterns):
+def _answer_question(stdout: bytes, proc, qa_patterns, qa_wait_patterns) -> bool:
     """
     Private helper function to try and answer questions raised in interactive shell commands.
     """
@@ -374,10 +376,15 @@ def _answer_question(stdout, proc, qa_patterns, qa_wait_patterns):
 
 
 @run_shell_cmd_cache
-def run_shell_cmd(cmd, fail_on_error=True, split_stderr=False, stdin=None, env=None,
-                  hidden=False, in_dry_run=False, verbose_dry_run=False, work_dir=None, use_bash=True,
-                  output_file=True, stream_output=None, asynchronous=False, task_id=None, with_hooks=True,
-                  qa_patterns=None, qa_wait_patterns=None, qa_timeout=100, log_output_on_success=True):
+def run_shell_cmd(cmd: Any, fail_on_error: bool = True, split_stderr: bool = False,
+                  stdin: Optional[Any] = None, env: Optional[dict] = None,
+                  hidden: bool = False, in_dry_run: bool = False, verbose_dry_run: bool = False,
+                  work_dir: Optional[str] = None, use_bash: bool = True,
+                  output_file: bool = True, stream_output: Optional[Any] = None,
+                  asynchronous: bool = False, task_id: Optional[Any] = None,
+                  with_hooks: bool = True, qa_patterns: Optional[Sequence[Tuple[Any, Any]]] = None,
+                  qa_wait_patterns: Optional[Sequence[str]] = None, qa_timeout: int = 100,
+                  log_output_on_success: bool = True) -> RunShellCmdResult:
     """
     Run specified (interactive) shell command, and capture output + exit code.
 
diff --git a/easybuild/tools/toolchain/compiler.py b/easybuild/tools/toolchain/compiler.py
index 32a7960c1f..4af4fb9da6 100644
--- a/easybuild/tools/toolchain/compiler.py
+++ b/easybuild/tools/toolchain/compiler.py
@@ -31,6 +31,8 @@
 * Kenneth Hoste (Ghent University)
 * Damian Alvarez (Forschungszentrum Juelich GmbH)
 """
+from typing import List
+
 from easybuild.tools import systemtools
 from easybuild.tools.build_log import EasyBuildError, print_warning
 from easybuild.tools.config import build_option
@@ -133,13 +135,13 @@ class Compiler(Toolchain):
     COMPILER_CC = None
     COMPILER_CXX = None
     COMPILER_C_OPTIONS = ['cstd']
-    COMPILER_C_UNIQUE_OPTIONS = []
+    COMPILER_C_UNIQUE_OPTIONS: List[str] = []
 
     COMPILER_F77 = None
     COMPILER_F90 = None
     COMPILER_FC = None
     COMPILER_F_OPTIONS = ['i8', 'r8']
-    COMPILER_F_UNIQUE_OPTIONS = []
+    COMPILER_F_UNIQUE_OPTIONS: List[str] = []
 
     LINKERS = None
     LINKER_TOGGLE_STATIC_DYNAMIC = None
diff --git a/easybuild/tools/toolchain/linalg.py b/easybuild/tools/toolchain/linalg.py
index 2e94f513d0..297528cfac 100644
--- a/easybuild/tools/toolchain/linalg.py
+++ b/easybuild/tools/toolchain/linalg.py
@@ -31,6 +31,8 @@
 * Kenneth Hoste (Ghent University)
 """
 
+from typing import Dict, Optional
+
 from easybuild.tools.build_log import EasyBuildError
 from easybuild.tools.toolchain.toolchain import Toolchain
 
@@ -43,7 +45,7 @@ class LinAlg(Toolchain):
     BLAS_MODULE_NAME = None
     BLAS_LIB = None
     BLAS_LIB_MT = None
-    BLAS_LIB_MAP = {}
+    BLAS_LIB_MAP: Dict[str, Optional[str]] = {}
     BLAS_LIB_GROUP = False
     BLAS_LIB_STATIC = False
     BLAS_LIB_DIR = ['lib']
@@ -74,7 +76,7 @@ class LinAlg(Toolchain):
     SCALAPACK_REQUIRES = ['LIBBLACS', 'LIBLAPACK', 'LIBBLAS']
     SCALAPACK_LIB = None
     SCALAPACK_LIB_MT = None
-    SCALAPACK_LIB_MAP = {}
+    SCALAPACK_LIB_MAP: Dict[str, Optional[str]] = {}
     SCALAPACK_LIB_GROUP = False
     SCALAPACK_LIB_STATIC = False
     SCALAPACK_LIB_DIR = ['lib']
diff --git a/easybuild/tools/toolchain/toolchain.py b/easybuild/tools/toolchain/toolchain.py
index f4ce06b334..94ae4674e8 100644
--- a/easybuild/tools/toolchain/toolchain.py
+++ b/easybuild/tools/toolchain/toolchain.py
@@ -70,6 +70,7 @@
 from easybuild.tools.toolchain.options import ToolchainOptions
 from easybuild.tools.toolchain.toolchainvariables import ToolchainVariables
 from easybuild.tools.utilities import nub, unique_ordered_extend, trace_msg
+from typing import Any, Dict
 
 
 _log = fancylogger.getLogger('tools.toolchain', fname=False)
@@ -166,7 +167,7 @@ class Toolchain:
 
     # list of class 'constants' that should be restored for every new instance of this class
     CLASS_CONSTANTS_TO_RESTORE = None
-    CLASS_CONSTANT_COPIES = {}
+    CLASS_CONSTANT_COPIES: Dict[str, Any] = {}
 
     @classmethod
     def _is_toolchain_for(cls, name):
diff --git a/easybuild/tools/toolchain/utilities.py b/easybuild/tools/toolchain/utilities.py
index e0dabe0061..587bf14532 100644
--- a/easybuild/tools/toolchain/utilities.py
+++ b/easybuild/tools/toolchain/utilities.py
@@ -38,6 +38,7 @@
 import copy
 import re
 import sys
+from typing import Any, Dict
 
 import easybuild.tools.toolchain
 from easybuild.tools.entrypoints import EntrypointToolchain
@@ -49,7 +50,7 @@
 
 TC_CONST_PREFIX = 'TC_CONSTANT_'
 
-_initial_toolchain_instances = {}
+_initial_toolchain_instances: Dict[str, Any] = {}
 
 _log = fancylogger.getLogger("toolchain.utilities")
 
diff --git a/easybuild/tools/utilities.py b/easybuild/tools/utilities.py
index 8369bc023c..89af564eff 100644
--- a/easybuild/tools/utilities.py
+++ b/easybuild/tools/utilities.py
@@ -36,6 +36,8 @@
 import sys
 from string import ascii_letters, digits
 
+from typing import Any, Callable, Dict, Iterable, List, Optional, Union
+
 from easybuild.base import fancylogger
 from easybuild.tools.build_log import EasyBuildError, print_msg
 from easybuild.tools.config import build_option
@@ -47,15 +49,16 @@
 INDENT_4SPACES = ' ' * 4
 
 
-def flatten(lst):
+def flatten(lst: Iterable[Iterable[Any]]) -> List[Any]:
     """Flatten a list of lists."""
-    res = []
+    res: List[Any] = []
     for x in lst:
         res.extend(x)
     return res
 
 
-def quote_str(val, escape_newline=False, prefer_single_quotes=False, escape_backslash=False, tcl=False):
+def quote_str(val, escape_newline: bool = False, prefer_single_quotes: bool = False,
+              escape_backslash: bool = False, tcl: bool = False):
     """
     Obtain a new value to be used in string replacement context.
 
@@ -105,7 +108,7 @@ def quote_py_str(val):
     return quote_str(val, escape_newline=True, prefer_single_quotes=True, escape_backslash=True)
 
 
-def shell_quote(token):
+def shell_quote(token) -> str:
     """
     Wrap provided token in single quotes (to escape space and characters with special meaning in a shell),
     so it can be used in a shell command. This results in token that is not expanded/interpolated by the shell.
@@ -117,7 +120,7 @@ def shell_quote(token):
     return "'%s'" % re.sub(r"(?<!\\)'", r"\'", token)
 
 
-def remove_unwanted_chars(inputstring):
+def remove_unwanted_chars(inputstring: str) -> str:
     """Remove unwanted characters from the given string and return a copy
 
     All non-letter and non-numeral characters are considered unwanted except for underscore ('_').
@@ -132,7 +135,7 @@ def capitalize_first_letter(string: str) -> str:
     return string[0].upper() + string[1:]
 
 
-def import_available_modules(namespace):
+def import_available_modules(namespace: str) -> list:
     """
     Import all available module in the specified namespace.
 
@@ -165,7 +168,8 @@ def import_available_modules(namespace):
     return modules
 
 
-def only_if_module_is_available(modnames, pkgname=None, url=None):
+def only_if_module_is_available(modnames: Union[str, Iterable[str]], pkgname: Optional[str] = None,
+                                url: Optional[str] = None) -> Callable[[Callable[..., Any]], Callable[..., Any]]:
     """Decorator to guard functions/methods against missing required module with specified name."""
     if pkgname and url is None:
         url = 'https://pypi.python.org/pypi/%s' % pkgname
@@ -173,7 +177,7 @@ def only_if_module_is_available(modnames, pkgname=None, url=None):
     if isinstance(modnames, str):
         modnames = (modnames,)
 
-    def wrap(orig):
+    def wrap(orig: Callable[..., Any]) -> Callable[..., Any]:
         """Decorated function, raises ImportError if specified module is not available."""
         try:
             imported = None
@@ -204,13 +208,13 @@ def error(*args, **kwargs):
     return wrap
 
 
-def trace_msg(message, silent=False):
+def trace_msg(message: Any, silent: bool = False) -> None:
     """Print trace message."""
     if build_option('trace'):
         print_msg('  >> ' + message, prefix=False)
 
 
-def nub(list_):
+def nub(list_: list) -> list:
     """Returns the unique items of a list of hashables, while preserving order of the original list,
     i.e. the first unique element encoutered is retained.
 
@@ -225,7 +229,7 @@ def nub(list_):
     return list(dict.fromkeys(list_))
 
 
-def unique_ordered_extend(base, affix):
+def unique_ordered_extend(base: list, affix: list) -> list:
     """Extend base list with elements of affix list keeping order and without duplicates"""
     if isinstance(affix, str):
         # avoid extending with strings, as iterables generate wrong result without error
@@ -242,7 +246,7 @@ def unique_ordered_extend(base, affix):
     return nub(ext_base)  # remove duplicates
 
 
-def get_class_for(modulepath, class_name):
+def get_class_for(modulepath: str, class_name: str) -> type:
     """
     Get class for a given Python class name and Python module path.
 
@@ -262,9 +266,9 @@ def get_class_for(modulepath, class_name):
     return klass
 
 
-def get_subclasses_dict(klass, include_base_class=False):
+def get_subclasses_dict(klass: type, include_base_class: bool = False) -> Dict[type, List[type]]:
     """Get dict with subclasses per classes, recursively from the specified base class."""
-    res = {}
+    res: Dict[type, List[type]] = {}
     subclasses = klass.__subclasses__()
     if include_base_class:
         res.update({klass: subclasses})
@@ -274,12 +278,12 @@ def get_subclasses_dict(klass, include_base_class=False):
     return res
 
 
-def get_subclasses(klass, include_base_class=False):
+def get_subclasses(klass: type, include_base_class: bool = False) -> Iterable[type]:
     """Get list of all subclasses, recursively from the specified base class."""
     return get_subclasses_dict(klass, include_base_class=include_base_class).keys()
 
 
-def mk_md_table(titles, columns):
+def mk_md_table(titles: Iterable[str], columns: Iterable[Iterable[str]]) -> List[str]:
     """
     Returns a MarkDown table with given titles and columns (a nested list of string columns for each column)
     """
@@ -315,7 +319,7 @@ def mk_md_table(titles, columns):
     return table
 
 
-def mk_rst_table(titles, columns):
+def mk_rst_table(titles: Iterable[str], columns: Iterable[Iterable[str]]) -> List[str]:
     """
     Returns an rst table with given titles and columns (a nested list of string columns for each column)
     """
@@ -354,7 +358,7 @@ def mk_rst_table(titles, columns):
     return table
 
 
-def time2str(delta):
+def time2str(delta: datetime.timedelta) -> str:
     """Return string representing provided datetime.timedelta value in human-readable form."""
     res = None
 
@@ -376,8 +380,8 @@ def time2str(delta):
     return ' '.join(res)
 
 
-def natural_keys(key):
+def natural_keys(key: str) -> List[Any]:
     """Can be used as the sort key in list.sort(key=natural_keys) to sort in natural order (i.e. respecting numbers)"""
-    def try_to_int(key_part):
+    def try_to_int(key_part: str) -> Any:
         return int(key_part) if key_part.isdigit() else key_part
     return [try_to_int(key_part) for key_part in re.split(r'(\d+)', key)]
diff --git a/easybuild/tools/variables.py b/easybuild/tools/variables.py
index 6f81e198de..0d7905e183 100644
--- a/easybuild/tools/variables.py
+++ b/easybuild/tools/variables.py
@@ -33,6 +33,7 @@
 """
 import copy
 import os
+from typing import Any, Dict, Iterable, List, Optional
 
 from easybuild.base import fancylogger
 from easybuild.tools.build_log import EasyBuildError
@@ -41,7 +42,7 @@
 _log = fancylogger.getLogger('variables', fname=False)
 
 
-def get_class(name, default_class, map_class=None):
+def get_class(name: Optional[str], default_class: type, map_class: Optional[Dict[Any, Any]] = None) -> type:
     """Return class based on default
         map_class
              if key == str -> value = class
@@ -63,7 +64,7 @@ def get_class(name, default_class, map_class=None):
     return klass
 
 
-def join_map_class(map_classes):
+def join_map_class(map_classes: Iterable[Dict[Any, Any]]) -> Dict[Any, Any]:
     """Join all class_maps into single class_map"""
     res = {}
     for map_class in map_classes:
@@ -100,27 +101,27 @@ class StrList(list):
 
     JOIN_BEGIN_END = False
 
-    def __init__(self, *args, **kwargs):
+    def __init__(self, *args, **kwargs) -> None:
         super().__init__(*args, **kwargs)
         self.log = fancylogger.getLogger(self.__class__.__name__, fname=False)
 
-    def str_convert(self, x):
+    def str_convert(self, x) -> str:
         """Convert members of list to string (no prefix of begin and end)"""
         return ''.join([str(y) for y in [self.PREFIX, str(x), self.SUFFIX] if y is not None])
 
-    def _str_ok(self, x):
+    def _str_ok(self, x) -> bool:
         """Test if x can be added to returned string"""
         test = x is not None and len(str(x)) > 0
         return test
 
-    def _str_self(self):
+    def _str_self(self) -> List[str]:
         """Main part of __str__"""
         return [self.str_convert(x) for x in self if self._str_ok(x)]
 
-    def sanitize(self):
+    def sanitize(self) -> None:
         """Sanitize self"""
 
-    def __str__(self):
+    def __str__(self) -> str:
         """_str_self and support for BEGIN/END"""
         self.sanitize()
         xs = [self.BEGIN] + self._str_self() + [self.END]
@@ -135,11 +136,11 @@ def __getattribute__(self, attr_name):
         else:
             return super().__getattribute__(attr_name)
 
-    def copy(self):
+    def copy(self) -> Any:
         """Return copy of self"""
         return copy.deepcopy(self)
 
-    def try_remove(self, values):
+    def try_remove(self, values: Iterable[Any]) -> None:
         """Remove without ValueError in case of missing element"""
         for value in values:
             try:
@@ -206,9 +207,9 @@ def append_subdirs(self, base, subdirs=None):
 class ListOfLists(list):
     """List of lists"""
     DEFAULT_CLASS = StrList
-    PROTECTED_CLASSES = []  # classes that are not converted to DEFAULT_CLASS
+    PROTECTED_CLASSES: List[type] = []  # classes that are not converted to DEFAULT_CLASS
     # PROTECTED_INSTANCES = [AbsPathList, LibraryList]
-    PROTECTED_INSTANCES = []
+    PROTECTED_INSTANCES: List[type] = []
     PROTECT_CLASS_SELF = True  # don't convert values that are same class as DEFAULT_CLASS
     PROTECT_INSTANCE_SELF = True  # don't convert values that are instance of DEFAULT_CLASS
 
@@ -451,10 +452,11 @@ class Variables(dict):
             but are in different classes
     """
     DEFAULT_LISTCLASS = ListOfLists
-    MAP_LISTCLASS = {}  # map between variable name and ListOfList classes (ie not the (default) class for the variable)
-
+    # map between variable name and ListOfList classes (ie not the (default) class for the variable)
+    MAP_LISTCLASS: Dict[str, type] = {}
     DEFAULT_CLASS = StrList
-    MAP_CLASS = {}  # predefined map to specify (default) mapping between variables and classes
+    # predefined map to specify (default) mapping between variables and classes
+    MAP_CLASS: Dict[str, type] = {}
 
     def __init__(self, *args, **kwargs):
         super().__init__(*args, **kwargs)
diff --git a/easybuild/tools/version.py b/easybuild/tools/version.py
index c4fbae9e89..42b69b8e61 100644
--- a/easybuild/tools/version.py
+++ b/easybuild/tools/version.py
@@ -34,8 +34,10 @@
 * Jens Timmerman (Ghent University)
 """
 import os
-from easybuild.tools import LooseVersion
 from socket import gethostname
+from typing import Any
+
+from easybuild.tools import LooseVersion
 
 # note: release candidates should be versioned as a pre-release, e.g. "1.1rc1"
 # 1.1-rc1 would indicate a post-release, i.e., and update of 1.1, so beware!
@@ -50,7 +52,7 @@
 UNKNOWN_EASYBLOCKS_VERSION = '0.0.UNKNOWN.EASYBLOCKS'
 
 
-def get_git_revision():
+def get_git_revision() -> str:
     """
     Returns the git revision (e.g. aab4afc016b742c6d4b157427e192942d0e131fe),
     or UNKNOWN is getting the git revision fails
@@ -91,7 +93,7 @@ def get_git_revision():
     EASYBLOCKS_VERSION = UNKNOWN_EASYBLOCKS_VERSION  # make sure it is smaller then anything
 
 
-def this_is_easybuild():
+def this_is_easybuild() -> str:
     """Standard starting message"""
     top_version = max(FRAMEWORK_VERSION, LooseVersion(EASYBLOCKS_VERSION))
     msg = "This is EasyBuild %s (framework: %s, easyblocks: %s) on host %s."
@@ -105,7 +107,7 @@ def this_is_easybuild():
     return msg
 
 
-def different_major_versions(v1, v2):
+def different_major_versions(v1: Any, v2: Any) -> bool:
     """Compare major versions"""
     # Deal with version instances being either strings or LooseVersion
     if isinstance(v1, str):
diff --git a/mypy.ini b/mypy.ini
new file mode 100644
index 0000000000..87cfbc1a31
--- /dev/null
+++ b/mypy.ini
@@ -0,0 +1,34 @@
+[mypy]
+# Core settings
+python_version = 3.6
+warn_return_any = False
+warn_unused_configs = True
+
+# Ignore missing imports - EasyBuild uses dynamic imports extensively
+ignore_missing_imports = True
+
+# Don't check untyped calls or definitions - we're focusing on existing type hints
+# and improving them, not adding them everywhere
+check_untyped_defs = False
+disallow_untyped_defs = False
+
+# Don't warn about anything related to dynamically created imports/attributes
+warn_no_return = False
+warn_unreachable = False
+strict_optional = False
+
+# Show error codes to identify problems
+show_error_codes = True
+show_column_numbers = True
+
+# For subclass patterns and inheritance
+warn_redundant_casts = True
+warn_unused_ignores = True
+
+[mypy-easybuild.*]
+# Apply stricter checks to the main codebase
+warn_return_any = True
+
+[mypy-test.*]
+# Less strict for tests
+ignore_errors = True