diff --git a/.gitignore b/.gitignore
index 83ff4ab4..b8f29c5e 100644
--- a/.gitignore
+++ b/.gitignore
@@ -106,4 +106,11 @@ env3?/
 # MyPy cache
 .mypy_cache/
 
+# Output cache for setup.py checker
 all_known_setup.yaml
+
+# mkdocs
+site/
+
+# Virtual environments
+venv*
diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 4e4c9a14..59ddddee 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -20,7 +20,7 @@ repos:
   rev: 20.8b1
   hooks:
   - id: black
-    files: ^bin/update_pythons.py$
+    files: ^bin/update_pythons.py|setup.py$
 
 - repo: https://github.com/pre-commit/mirrors-mypy
   rev: v0.800
diff --git a/.readthedocs.yml b/.readthedocs.yml
index 21c669a9..b59f4199 100644
--- a/.readthedocs.yml
+++ b/.readthedocs.yml
@@ -6,9 +6,9 @@ mkdocs:
   configuration: mkdocs.yml
 
 python:
-  version: 3.7
+  version: 3.8
   install:
     - method: pip
       path: .
       extra_requirements:
-        - dev
+        - docs
diff --git a/docs/options.md b/docs/options.md
index fecbe23e..7cba035b 100644
--- a/docs/options.md
+++ b/docs/options.md
@@ -356,27 +356,26 @@ CIBW_BEFORE_BUILD: "{package}/script/prepare_for_build.sh"
 ```
 
 !!! note
-    If you need dependencies installed for the build, we recommend using pyproject.toml. This is an example pyproject.toml file:
+    If you need dependencies installed for the build, we recommend using
+    `pyproject.toml`. This is an example `pyproject.toml` file:
 
         [build-system]
         requires = [
             "setuptools>=42",
             "wheel",
             "Cython",
-            "numpy==1.11.3; python_version<='3.6'",
-            "numpy==1.14.5; python_version=='3.7'",
-            "numpy==1.17.3; python_version=='3.8'",
-            "numpy==1.19.4; python_version>='3.9'",
+            "numpy==1.13.3; python_version<'3.5'",
+            "oldest-supported-numpy; python_version>='3.5'",
         ]
 
         build-backend = "setuptools.build_meta"
 
-    This [PEP 517][]/[PEP 518][] style build allows you to completely control the
-    build environment in cibuildwheel, [PyPA-build][], and pip, doesn't force
-    downstream users to install anything they don't need, and lets you do more
-    complex pinning (Cython, for example, requires a wheel to be built with an
-    equal or earlier version of NumPy; pinning in this way is the only way to
-    ensure your module works on all available NumPy versions).
+    This [PEP 517][]/[PEP 518][] style build allows you to completely control
+    the build environment in cibuildwheel, [PyPA-build][], and pip, doesn't
+    force downstream users to install anything they don't need, and lets you do
+    more complex pinning (Cython, for example, requires a wheel to be built
+    with an equal or earlier version of NumPy; pinning in this way is the only
+    way to ensure your module works on all available NumPy versions).
 
     [PyPA-build]: https://pypa-build.readthedocs.io/en/latest/
     [PEP 517]: https://www.python.org/dev/peps/pep-0517/
diff --git a/examples/github-deploy.yml b/examples/github-deploy.yml
index 1d025814..b83c4bbd 100644
--- a/examples/github-deploy.yml
+++ b/examples/github-deploy.yml
@@ -16,7 +16,7 @@ jobs:
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        os: [ubuntu-18.04, windows-2019, macos-10.15]
+        os: [ubuntu-20.04, windows-2019, macos-10.15]
 
     steps:
       - uses: actions/checkout@v2
diff --git a/examples/github-minimal.yml b/examples/github-minimal.yml
index 07d52495..03ce1724 100644
--- a/examples/github-minimal.yml
+++ b/examples/github-minimal.yml
@@ -8,7 +8,7 @@ jobs:
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        os: [ubuntu-18.04, windows-2019, macos-10.15]
+        os: [ubuntu-20.04, windows-2019, macos-10.15]
 
     steps:
       - uses: actions/checkout@v2
diff --git a/examples/github-with-qemu.yml b/examples/github-with-qemu.yml
index f04aac3d..2b3f55af 100644
--- a/examples/github-with-qemu.yml
+++ b/examples/github-with-qemu.yml
@@ -8,7 +8,7 @@ jobs:
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        os: [ubuntu-18.04, windows-2019, macos-10.15]
+        os: [ubuntu-20.04, windows-2019, macos-10.15]
 
     steps:
       - uses: actions/checkout@v2
diff --git a/requirements-dev.txt b/requirements-dev.txt
index aefbcb6d..18dc383f 100644
--- a/requirements-dev.txt
+++ b/requirements-dev.txt
@@ -1 +1 @@
--e .[dev]
+-e .[dev,docs]
diff --git a/setup.cfg b/setup.cfg
index 9f8602b1..89d0ec02 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -38,23 +38,6 @@ install_requires =
 [options.package_data]
 cibuildwheel = resources/*
 
-[options.extras_require]
-dev =
-    click
-    mkdocs-include-markdown-plugin==2.1.1
-    mkdocs==1.0.4
-    pip-tools
-    pygithub
-    ghapi
-    pymdown-extensions
-    pytest>=4
-    pytest-timeout
-    pyyaml
-    requests
-    typing-extensions
-    rich>=9.6
-    mypy>=0.800
-
 [options.packages.find]
 include =
     cibuildwheel
diff --git a/setup.py b/setup.py
index 60684932..bf34fe94 100644
--- a/setup.py
+++ b/setup.py
@@ -1,3 +1,31 @@
 from setuptools import setup
 
-setup()
+extras = {
+    "docs": [
+        "mkdocs-include-markdown-plugin==2.1.1",
+        "mkdocs==1.0.4",
+        "pymdown-extensions",
+    ],
+    "test": [
+        "jinja2",
+        "pytest>=4",
+        "pytest-timeout",
+    ],
+    "dev": [
+        "click",
+        "ghapi",
+        "mypy>=0.800",
+        "packaging>=20.8",
+        "pip-tools",
+        "pygithub",
+        "pyyaml",
+        "requests",
+        "rich>=9.6",
+        "typing-extensions",
+    ],
+}
+
+extras["all"] = sum(extras.values(), [])
+extras["dev"] += extras["test"]
+
+setup(extras_require=extras)