diff --git a/src/_pytest/capture.py b/src/_pytest/capture.py
index 13931ca10..bcc16ceb6 100644
--- a/src/_pytest/capture.py
+++ b/src/_pytest/capture.py
@@ -9,9 +9,11 @@ import os
 import sys
 from io import UnsupportedOperation
 from tempfile import TemporaryFile
+from typing import Generator
 from typing import Optional
 from typing import TextIO
 from typing import Tuple
+from typing import Union
 
 import pytest
 from _pytest.compat import TYPE_CHECKING
@@ -46,7 +48,7 @@ def pytest_addoption(parser: Parser) -> None:
     )
 
 
-def _colorama_workaround():
+def _colorama_workaround() -> None:
     """
     Ensure colorama is imported so that it attaches to the correct stdio
     handles on Windows.
@@ -62,7 +64,7 @@ def _colorama_workaround():
             pass
 
 
-def _readline_workaround():
+def _readline_workaround() -> None:
     """
     Ensure readline is imported so that it attaches to the correct stdio
     handles on Windows.
@@ -87,7 +89,7 @@ def _readline_workaround():
             pass
 
 
-def _py36_windowsconsoleio_workaround(stream):
+def _py36_windowsconsoleio_workaround(stream: TextIO) -> None:
     """
     Python 3.6 implemented unicode console handling for Windows. This works
     by reading/writing to the raw console handle using
@@ -202,7 +204,7 @@ class TeeCaptureIO(CaptureIO):
         self._other = other
         super().__init__()
 
-    def write(self, s) -> int:
+    def write(self, s: str) -> int:
         super().write(s)
         return self._other.write(s)
 
@@ -222,13 +224,13 @@ class DontReadFromInput:
     def __iter__(self):
         return self
 
-    def fileno(self):
+    def fileno(self) -> int:
         raise UnsupportedOperation("redirected stdin is pseudofile, has no fileno()")
 
-    def isatty(self):
+    def isatty(self) -> bool:
         return False
 
-    def close(self):
+    def close(self) -> None:
         pass
 
     @property
@@ -251,7 +253,7 @@ class SysCaptureBinary:
 
     EMPTY_BUFFER = b""
 
-    def __init__(self, fd, tmpfile=None, *, tee=False):
+    def __init__(self, fd: int, tmpfile=None, *, tee: bool = False) -> None:
         name = patchsysdict[fd]
         self._old = getattr(sys, name)
         self.name = name
@@ -288,7 +290,7 @@ class SysCaptureBinary:
             op, self._state, ", ".join(states)
         )
 
-    def start(self):
+    def start(self) -> None:
         self._assert_state("start", ("initialized",))
         setattr(sys, self.name, self.tmpfile)
         self._state = "started"
@@ -301,7 +303,7 @@ class SysCaptureBinary:
         self.tmpfile.truncate()
         return res
 
-    def done(self):
+    def done(self) -> None:
         self._assert_state("done", ("initialized", "started", "suspended", "done"))
         if self._state == "done":
             return
@@ -310,19 +312,19 @@ class SysCaptureBinary:
         self.tmpfile.close()
         self._state = "done"
 
-    def suspend(self):
+    def suspend(self) -> None:
         self._assert_state("suspend", ("started", "suspended"))
         setattr(sys, self.name, self._old)
         self._state = "suspended"
 
-    def resume(self):
+    def resume(self) -> None:
         self._assert_state("resume", ("started", "suspended"))
         if self._state == "started":
             return
         setattr(sys, self.name, self.tmpfile)
         self._state = "started"
 
-    def writeorg(self, data):
+    def writeorg(self, data) -> None:
         self._assert_state("writeorg", ("started", "suspended"))
         self._old.flush()
         self._old.buffer.write(data)
@@ -352,7 +354,7 @@ class FDCaptureBinary:
 
     EMPTY_BUFFER = b""
 
-    def __init__(self, targetfd):
+    def __init__(self, targetfd: int) -> None:
         self.targetfd = targetfd
 
         try:
@@ -369,7 +371,9 @@ class FDCaptureBinary:
             # Further complications are the need to support suspend() and the
             # possibility of FD reuse (e.g. the tmpfile getting the very same
             # target FD). The following approach is robust, I believe.
-            self.targetfd_invalid = os.open(os.devnull, os.O_RDWR)
+            self.targetfd_invalid = os.open(
+                os.devnull, os.O_RDWR
+            )  # type: Optional[int]
             os.dup2(self.targetfd_invalid, targetfd)
         else:
             self.targetfd_invalid = None
@@ -380,7 +384,8 @@ class FDCaptureBinary:
             self.syscapture = SysCapture(targetfd)
         else:
             self.tmpfile = EncodedFile(
-                TemporaryFile(buffering=0),
+                # TODO: Remove type ignore, fixed in next mypy release.
+                TemporaryFile(buffering=0),  # type: ignore[arg-type]
                 encoding="utf-8",
                 errors="replace",
                 write_through=True,
@@ -392,7 +397,7 @@ class FDCaptureBinary:
 
         self._state = "initialized"
 
-    def __repr__(self):
+    def __repr__(self) -> str:
         return "<{} {} oldfd={} _state={!r} tmpfile={!r}>".format(
             self.__class__.__name__,
             self.targetfd,
@@ -408,7 +413,7 @@ class FDCaptureBinary:
             op, self._state, ", ".join(states)
         )
 
-    def start(self):
+    def start(self) -> None:
         """ Start capturing on targetfd using memorized tmpfile. """
         self._assert_state("start", ("initialized",))
         os.dup2(self.tmpfile.fileno(), self.targetfd)
@@ -423,7 +428,7 @@ class FDCaptureBinary:
         self.tmpfile.truncate()
         return res
 
-    def done(self):
+    def done(self) -> None:
         """ stop capturing, restore streams, return original capture file,
         seeked to position zero. """
         self._assert_state("done", ("initialized", "started", "suspended", "done"))
@@ -439,7 +444,7 @@ class FDCaptureBinary:
         self.tmpfile.close()
         self._state = "done"
 
-    def suspend(self):
+    def suspend(self) -> None:
         self._assert_state("suspend", ("started", "suspended"))
         if self._state == "suspended":
             return
@@ -447,7 +452,7 @@ class FDCaptureBinary:
         os.dup2(self.targetfd_save, self.targetfd)
         self._state = "suspended"
 
-    def resume(self):
+    def resume(self) -> None:
         self._assert_state("resume", ("started", "suspended"))
         if self._state == "started":
             return
@@ -497,12 +502,12 @@ class MultiCapture:
         self.out = out
         self.err = err
 
-    def __repr__(self):
+    def __repr__(self) -> str:
         return "<MultiCapture out={!r} err={!r} in_={!r} _state={!r} _in_suspended={!r}>".format(
             self.out, self.err, self.in_, self._state, self._in_suspended,
         )
 
-    def start_capturing(self):
+    def start_capturing(self) -> None:
         self._state = "started"
         if self.in_:
             self.in_.start()
@@ -520,7 +525,7 @@ class MultiCapture:
             self.err.writeorg(err)
         return out, err
 
-    def suspend_capturing(self, in_=False):
+    def suspend_capturing(self, in_: bool = False) -> None:
         self._state = "suspended"
         if self.out:
             self.out.suspend()
@@ -530,7 +535,7 @@ class MultiCapture:
             self.in_.suspend()
             self._in_suspended = True
 
-    def resume_capturing(self):
+    def resume_capturing(self) -> None:
         self._state = "resumed"
         if self.out:
             self.out.resume()
@@ -540,7 +545,7 @@ class MultiCapture:
             self.in_.resume()
             self._in_suspended = False
 
-    def stop_capturing(self):
+    def stop_capturing(self) -> None:
         """ stop capturing and reset capturing streams """
         if self._state == "stopped":
             raise ValueError("was already stopped")
@@ -596,15 +601,15 @@ class CaptureManager:
 
     def __init__(self, method: "_CaptureMethod") -> None:
         self._method = method
-        self._global_capturing = None
+        self._global_capturing = None  # type: Optional[MultiCapture]
         self._capture_fixture = None  # type: Optional[CaptureFixture]
 
-    def __repr__(self):
+    def __repr__(self) -> str:
         return "<CaptureManager _method={!r} _global_capturing={!r} _capture_fixture={!r}>".format(
             self._method, self._global_capturing, self._capture_fixture
         )
 
-    def is_capturing(self):
+    def is_capturing(self) -> Union[str, bool]:
         if self.is_globally_capturing():
             return "global"
         if self._capture_fixture:
@@ -613,40 +618,41 @@ class CaptureManager:
 
     # Global capturing control
 
-    def is_globally_capturing(self):
+    def is_globally_capturing(self) -> bool:
         return self._method != "no"
 
-    def start_global_capturing(self):
+    def start_global_capturing(self) -> None:
         assert self._global_capturing is None
         self._global_capturing = _get_multicapture(self._method)
         self._global_capturing.start_capturing()
 
-    def stop_global_capturing(self):
+    def stop_global_capturing(self) -> None:
         if self._global_capturing is not None:
             self._global_capturing.pop_outerr_to_orig()
             self._global_capturing.stop_capturing()
             self._global_capturing = None
 
-    def resume_global_capture(self):
+    def resume_global_capture(self) -> None:
         # During teardown of the python process, and on rare occasions, capture
         # attributes can be `None` while trying to resume global capture.
         if self._global_capturing is not None:
             self._global_capturing.resume_capturing()
 
-    def suspend_global_capture(self, in_=False):
+    def suspend_global_capture(self, in_: bool = False) -> None:
         if self._global_capturing is not None:
             self._global_capturing.suspend_capturing(in_=in_)
 
-    def suspend(self, in_=False):
+    def suspend(self, in_: bool = False) -> None:
         # Need to undo local capsys-et-al if it exists before disabling global capture.
         self.suspend_fixture()
         self.suspend_global_capture(in_)
 
-    def resume(self):
+    def resume(self) -> None:
         self.resume_global_capture()
         self.resume_fixture()
 
     def read_global_capture(self):
+        assert self._global_capturing is not None
         return self._global_capturing.readouterr()
 
     # Fixture Control
@@ -665,30 +671,30 @@ class CaptureManager:
     def unset_fixture(self) -> None:
         self._capture_fixture = None
 
-    def activate_fixture(self):
+    def activate_fixture(self) -> None:
         """If the current item is using ``capsys`` or ``capfd``, activate them so they take precedence over
         the global capture.
         """
         if self._capture_fixture:
             self._capture_fixture._start()
 
-    def deactivate_fixture(self):
+    def deactivate_fixture(self) -> None:
         """Deactivates the ``capsys`` or ``capfd`` fixture of this item, if any."""
         if self._capture_fixture:
             self._capture_fixture.close()
 
-    def suspend_fixture(self):
+    def suspend_fixture(self) -> None:
         if self._capture_fixture:
             self._capture_fixture._suspend()
 
-    def resume_fixture(self):
+    def resume_fixture(self) -> None:
         if self._capture_fixture:
             self._capture_fixture._resume()
 
     # Helper context managers
 
     @contextlib.contextmanager
-    def global_and_fixture_disabled(self):
+    def global_and_fixture_disabled(self) -> Generator[None, None, None]:
         """Context manager to temporarily disable global and current fixture capturing."""
         self.suspend()
         try:
@@ -697,7 +703,7 @@ class CaptureManager:
             self.resume()
 
     @contextlib.contextmanager
-    def item_capture(self, when, item):
+    def item_capture(self, when: str, item: Item) -> Generator[None, None, None]:
         self.resume_global_capture()
         self.activate_fixture()
         try:
@@ -757,21 +763,21 @@ class CaptureFixture:
     fixtures.
     """
 
-    def __init__(self, captureclass, request):
+    def __init__(self, captureclass, request: SubRequest) -> None:
         self.captureclass = captureclass
         self.request = request
-        self._capture = None
+        self._capture = None  # type: Optional[MultiCapture]
         self._captured_out = self.captureclass.EMPTY_BUFFER
         self._captured_err = self.captureclass.EMPTY_BUFFER
 
-    def _start(self):
+    def _start(self) -> None:
         if self._capture is None:
             self._capture = MultiCapture(
                 in_=None, out=self.captureclass(1), err=self.captureclass(2),
             )
             self._capture.start_capturing()
 
-    def close(self):
+    def close(self) -> None:
         if self._capture is not None:
             out, err = self._capture.pop_outerr_to_orig()
             self._captured_out += out
@@ -793,18 +799,18 @@ class CaptureFixture:
         self._captured_err = self.captureclass.EMPTY_BUFFER
         return CaptureResult(captured_out, captured_err)
 
-    def _suspend(self):
+    def _suspend(self) -> None:
         """Suspends this fixture's own capturing temporarily."""
         if self._capture is not None:
             self._capture.suspend_capturing()
 
-    def _resume(self):
+    def _resume(self) -> None:
         """Resumes this fixture's own capturing temporarily."""
         if self._capture is not None:
             self._capture.resume_capturing()
 
     @contextlib.contextmanager
-    def disabled(self):
+    def disabled(self) -> Generator[None, None, None]:
         """Temporarily disables capture while inside the 'with' block."""
         capmanager = self.request.config.pluginmanager.getplugin("capturemanager")
         with capmanager.global_and_fixture_disabled():
@@ -815,7 +821,7 @@ class CaptureFixture:
 
 
 @pytest.fixture
-def capsys(request):
+def capsys(request: SubRequest):
     """Enable text capturing of writes to ``sys.stdout`` and ``sys.stderr``.
 
     The captured output is made available via ``capsys.readouterr()`` method
@@ -832,7 +838,7 @@ def capsys(request):
 
 
 @pytest.fixture
-def capsysbinary(request):
+def capsysbinary(request: SubRequest):
     """Enable bytes capturing of writes to ``sys.stdout`` and ``sys.stderr``.
 
     The captured output is made available via ``capsysbinary.readouterr()``
@@ -849,7 +855,7 @@ def capsysbinary(request):
 
 
 @pytest.fixture
-def capfd(request):
+def capfd(request: SubRequest):
     """Enable text capturing of writes to file descriptors ``1`` and ``2``.
 
     The captured output is made available via ``capfd.readouterr()`` method
@@ -866,7 +872,7 @@ def capfd(request):
 
 
 @pytest.fixture
-def capfdbinary(request):
+def capfdbinary(request: SubRequest):
     """Enable bytes capturing of writes to file descriptors ``1`` and ``2``.
 
     The captured output is made available via ``capfd.readouterr()`` method