diff --git a/.coveragerc b/.coveragerc
deleted file mode 100644
index 0ad0bd9e..00000000
--- a/.coveragerc
+++ /dev/null
@@ -1,6 +0,0 @@
-[run]
-omit =
-    tests/*
-    .tox/*
-    setup.py
-    *.egg/*
diff --git a/.flake8 b/.flake8
index 35a15583..f81cf2c7 100644
--- a/.flake8
+++ b/.flake8
@@ -1,6 +1,3 @@
 [flake8]
-ignore = E203, E266, E501, W503
-max-line-length = 80
-max-complexity = 18
-select = B,C,E,F,W,T4,B9
-exclude = docs/conf.py,.tox
+max-line-length = 79
+extend-ignore = E203, E501
diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index 0d78aa51..28b19a44 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -1,40 +1,101 @@
-# This workflow will install Python dependencies, run tests and lint with a variety of Python versions
-# For more information see: https://help.github.com/actions/language-and-framework-guides/using-python-with-github-actions
-
-name: Python package
+---
+name: CI
 
 on:
   push:
-    branches: [ master ]
+    branches: ["master"]
   pull_request:
-    branches: [ master ]
+    branches: ["master"]
+  workflow_dispatch:
 
 jobs:
-  build:
+  tests:
+    name: "Python ${{ matrix.python-version }} on ${{ matrix.platform }}"
+    runs-on: "${{ matrix.platform }}"
+    env:
+      USING_COVERAGE: '3.7,3.8'
 
-    runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: [3.5, 3.6, 3.7, 3.8]
+        platform: ["ubuntu-latest", "windows-latest"]
+        python-version: ["3.6", "3.7", "3.8"]
 
     steps:
-    - uses: actions/checkout@v2
-    - name: Set up Python ${{ matrix.python-version }}
-      uses: actions/setup-python@v1
-      with:
-        python-version: ${{ matrix.python-version }}
-    - name: Install dependencies
-      run: |
-        python -m pip install --upgrade pip
-        pip install -r requirements.txt
-    - name: Lint with flake8
-      run: |
-        pip install flake8
-        # stop the build if there are Python syntax errors or undefined names
-        flake8 . --count --select=E9,F63,F7,F82 --show-source --statistics
-        # exit-zero treats all errors as warnings. The GitHub editor is 127 chars wide
-        flake8 . --count --exit-zero --max-complexity=10 --max-line-length=127 --statistics
-    - name: Test with pytest
-      run: |
-        pip install pytest
-        pytest
+      - uses: "actions/checkout@v2"
+      - uses: "actions/setup-python@v2"
+        with:
+          python-version: "${{ matrix.python-version }}"
+
+      - name: "Install dependencies"
+        run: |
+          python -VV
+          python -m site
+          python -m pip install --upgrade pip setuptools wheel
+          python -m pip install --upgrade coverage[toml] virtualenv tox tox-gh-actions
+
+      - name: "Run tox targets for ${{ matrix.python-version }}"
+        run: "python -m tox"
+        env:
+          PLATFORM: ${{ matrix.platform }}
+
+      # We always use a modern Python version for combining coverage to prevent
+      # parsing errors in older versions for modern code.
+      - uses: "actions/setup-python@v2"
+        with:
+          python-version: "3.8"
+
+      - name: "Combine coverage"
+        run: |
+          set -xe
+          python -m pip install coverage[toml]
+          python -m coverage combine
+          python -m coverage xml
+        if: "contains(env.USING_COVERAGE, matrix.python-version) && matrix.platform == 'ubuntu-latest'"
+
+      - name: "Upload coverage to Codecov"
+        if: "contains(env.USING_COVERAGE, matrix.python-version) && matrix.platform == 'ubuntu-latest'"
+        uses: "codecov/codecov-action@v1"
+        with:
+          fail_ci_if_error: true
+
+  package:
+    name: "Build & verify package"
+    runs-on: "ubuntu-latest"
+
+    steps:
+      - uses: "actions/checkout@v2"
+      - uses: "actions/setup-python@v2"
+        with:
+          python-version: "3.8"
+
+      - name: "Install pep517 and twine"
+        run: "python -m pip install pep517 twine"
+
+      - name: "Build package"
+        run: "python -m pep517.build --source --binary ."
+
+      - name: "List result"
+        run: "ls -l dist"
+
+      - name: "Check long_description"
+        run: "python -m twine check dist/*"
+
+  install-dev:
+    strategy:
+      matrix:
+        os: ["ubuntu-latest", "windows-latest", "macos-latest"]
+
+    name: "Verify dev env"
+    runs-on: "${{ matrix.os }}"
+
+    steps:
+      - uses: "actions/checkout@v2"
+      - uses: "actions/setup-python@v2"
+        with:
+          python-version: "3.8"
+
+      - name: "Install in dev mode"
+        run: "python -m pip install -e .[dev]"
+
+      - name: "Import package"
+        run: "python -c 'import jwt; print(jwt.__version__)'"
diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 2617e46b..53c271ed 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -1,18 +1,18 @@
 repos:
   - repo: https://github.com/psf/black
-    rev: 19.3b0
+    rev: 19.10b0
     hooks:
       - id: black
-        language_version: python3.7
+        language_version: python3.8
 
   - repo: https://gitlab.com/pycqa/flake8
-    rev: 3.7.8
+    rev: 3.7.9
     hooks:
       - id: flake8
-        language_version: python3.7
+        language_version: python3.8
 
   - repo: https://github.com/asottile/seed-isort-config
-    rev: v1.9.3
+    rev: v1.9.4
     hooks:
       - id: seed-isort-config
 
@@ -21,10 +21,10 @@ repos:
     hooks:
       - id: isort
         additional_dependencies: [toml]
-        language_version: python3.7
+        language_version: python3.8
 
   - repo: https://github.com/pre-commit/pre-commit-hooks
-    rev: v2.3.0
+    rev: v2.4.0
     hooks:
       - id: trailing-whitespace
       - id: end-of-file-fixer
diff --git a/.travis.yml b/.travis.yml
deleted file mode 100644
index 5e2dd0c4..00000000
--- a/.travis.yml
+++ /dev/null
@@ -1,18 +0,0 @@
-language: python
-matrix:
-  include:
-    - python: 3.5
-      env: TOXENV=py35-crypto,py35-nocrypto,py35-contrib_crypto
-    - python: 3.6
-      env: TOXENV=py36-crypto,py36-nocrypto,py36-contrib_crypto
-    - python: 3.7
-      env: TOXENV=lint,typing,py37-crypto,py37-nocrypto,py37-contrib_crypto
-    - python: 3.8
-      env: TOXENV=py38-crypto,py38-nocrypto,py38-contrib_crypto
-install:
-  - pip install -U pip
-  - pip install -U tox coveralls
-script:
-  - tox
-after_success:
-  - coveralls
diff --git a/appveyor.yml b/appveyor.yml
deleted file mode 100644
index ac139e97..00000000
--- a/appveyor.yml
+++ /dev/null
@@ -1,38 +0,0 @@
-environment:
-  matrix:
-    - PYTHON: "C:\\Python35-x64"
-      TOX_ENV: "py35-crypto"
-
-    - PYTHON: "C:\\Python36-x64"
-      TOX_ENV: "py36-crypto"
-
-    - PYTHON: "C:\\Python37-x64"
-      TOX_ENV: "py37-crypto"
-
-init:
-  - SET PATH=%PYTHON%;%PATH%
-  - python -c "import sys;sys.stdout.write(sys.version)"
-  - ECHO .
-  - python -m pip list
-
-# pip & virtualenv are pre-installed
-install:
-  - python -m pip install -U setuptools
-  - python -m pip install -U pip
-  - python -m pip install -U wheel
-  - python -m pip install -U tox
-
-build: false  # Not a C# project, build stuff at the test step instead.
-
-test_script:
-  - python -m tox -e %TOX_ENV%
-
-after_test:
-  - python setup.py bdist_wheel
-  - ps: "ls dist"
-
-artifacts:
-  - path: dist\*
-
-#on_success:
-#  - TODO: upload the content of dist/*.whl to a public wheelhouse
diff --git a/codecov.yml b/codecov.yml
new file mode 100644
index 00000000..60a1e5c1
--- /dev/null
+++ b/codecov.yml
@@ -0,0 +1,10 @@
+---
+comment: false
+coverage:
+    status:
+        patch:
+            default:
+                target: "100"
+        project:
+            default:
+                target: "100"
diff --git a/docs/conf.py b/docs/conf.py
index 39f24b8a..42a978d9 100644
--- a/docs/conf.py
+++ b/docs/conf.py
@@ -1,38 +1,45 @@
-# PyJWT documentation build configuration file, created by
-# sphinx-quickstart on Thu Oct 22 18:11:10 2015.
-#
-# This file is execfile()d with the current directory set to its
-# containing dir.
-#
-# Note that not all possible configuration values are present in this
-# autogenerated file.
-#
-# All configuration values have a default; values that are commented out
-# serve to show the default.
-
+import codecs
 import os
 import re
-import shlex
-import sys
 
-# The theme to use for HTML and HTML Help pages.  See the documentation for
-# a list of builtin themes.
 import sphinx_rtd_theme
 
-# If extensions (or modules to document with autodoc) are in another directory,
-# add these directories to sys.path here. If the directory is relative to the
-# documentation root, use os.path.abspath to make it absolute, like shown here.
-# sys.path.insert(0, os.path.abspath('.'))
 
-# -- General configuration ------------------------------------------------
+def read(*parts):
+    """
+    Build an absolute path from *parts* and and return the contents of the
+    resulting file.  Assume UTF-8 encoding.
+    """
+    here = os.path.abspath(os.path.dirname(__file__))
+    with codecs.open(os.path.join(here, *parts), "rb", "utf-8") as f:
+        return f.read()
 
-# If your documentation needs a minimal Sphinx version, state it here.
-# needs_sphinx = '1.0'
+
+def find_version(*file_paths):
+    """
+    Build a path from *file_paths* and search for a ``__version__``
+    string inside.
+    """
+    version_file = read(*file_paths)
+    version_match = re.search(
+        r"^__version__ = ['\"]([^'\"]*)['\"]", version_file, re.M
+    )
+    if version_match:
+        return version_match.group(1)
+    raise RuntimeError("Unable to find version string.")
+
+
+# -- General configuration ------------------------------------------------
 
 # Add any Sphinx extension module names here, as strings. They can be
 # extensions coming with Sphinx (named 'sphinx.ext.*') or your custom
 # ones.
-extensions = []
+extensions = [
+    "sphinx.ext.autodoc",
+    "sphinx.ext.doctest",
+    "sphinx.ext.intersphinx",
+    "sphinx.ext.todo",
+]
 
 # Add any paths that contain templates here, relative to this directory.
 templates_path = ["_templates"]
@@ -42,9 +49,6 @@
 # source_suffix = ['.rst', '.md']
 source_suffix = ".rst"
 
-# The encoding of source files.
-# source_encoding = 'utf-8-sig'
-
 # The master toctree document.
 master_doc = "index"
 
@@ -57,19 +61,11 @@
 # |version| and |release|, also used in various other places throughout the
 # built documents.
 #
-# The short X.Y version.
-def get_version(package):
-    """
-    Return package version as listed in `__version__` in `init.py`.
-    """
-    with open(os.path.join("..", package, "__init__.py"), "rb") as init_py:
-        src = init_py.read().decode("utf-8")
-        return re.search("__version__ = ['\"]([^'\"]+)['\"]", src).group(1)
-
-
-version = get_version("jwt")
 # The full version, including alpha/beta/rc tags.
-release = version
+release = find_version("../jwt/__init__.py")
+
+# The short X.Y version.
+version = release.rsplit(u".", 1)[0]
 
 # The language for content autogenerated by Sphinx. Refer to documentation
 # for a list of supported languages.
@@ -78,40 +74,13 @@ def get_version(package):
 # Usually you set "language" from the command line for these cases.
 language = None
 
-# There are two options for replacing |today|: either, you set today to some
-# non-false value, then it is used:
-# today = ''
-# Else, today_fmt is used as the format for a strftime call.
-# today_fmt = '%B %d, %Y'
-
 # List of patterns, relative to source directory, that match files and
 # directories to ignore when looking for source files.
 exclude_patterns = ["_build"]
 
-# The reST default role (used for this markup: `text`) to use for all
-# documents.
-# default_role = None
-
-# If true, '()' will be appended to :func: etc. cross-reference text.
-# add_function_parentheses = True
-
-# If true, the current module name will be prepended to all description
-# unit titles (such as .. function::).
-# add_module_names = True
-
-# If true, sectionauthor and moduleauthor directives will be shown in the
-# output. They are ignored by default.
-# show_authors = False
-
 # The name of the Pygments (syntax highlighting) style to use.
 pygments_style = "sphinx"
 
-# A list of ignored prefixes for module index sorting.
-# modindex_common_prefix = []
-
-# If true, keep warnings as "system message" paragraphs in the built documents.
-# keep_warnings = False
-
 # If true, `todo` and `todoList` produce output, else they produce nothing.
 todo_include_todos = False
 
@@ -123,30 +92,6 @@ def get_version(package):
 
 html_theme_path = [sphinx_rtd_theme.get_html_theme_path()]
 
-# Theme options are theme-specific and customize the look and feel of a theme
-# further.  For a list of options available for each theme, see the
-# documentation.
-# html_theme_options = {}
-
-# Add any paths that contain custom themes here, relative to this directory.
-# html_theme_path = []
-
-# The name for this set of Sphinx documents.  If None, it defaults to
-# "<project> v<release> documentation".
-# html_title = None
-
-# A shorter title for the navigation bar.  Default is the same as html_title.
-# html_short_title = None
-
-# The name of an image file (relative to this directory) to place at the top
-# of the sidebar.
-# html_logo = None
-
-# The name of an image file (within the static path) to use as favicon of the
-# docs.  This file should be a Windows icon file (.ico) being 16x16 or 32x32
-# pixels large.
-# html_favicon = None
-
 # Add any paths that contain custom static files (such as style sheets) here,
 # relative to this directory. They are copied after the builtin static files,
 # so a file named "default.css" will overwrite the builtin "default.css".
@@ -159,118 +104,15 @@ def get_version(package):
     ]
 }
 
-# Add any extra paths that contain custom files (such as robots.txt or
-# .htaccess) here, relative to this directory. These files are copied
-# directly to the root of the documentation.
-# html_extra_path = []
-
-# If not '', a 'Last updated on:' timestamp is inserted at every page bottom,
-# using the given strftime format.
-# html_last_updated_fmt = '%b %d, %Y'
-
-# If true, SmartyPants will be used to convert quotes and dashes to
-# typographically correct entities.
-# html_use_smartypants = True
-
-# Custom sidebar templates, maps document names to template names.
-# html_sidebars = {}
-
-# Additional templates that should be rendered to pages, maps page names to
-# template names.
-# html_additional_pages = {}
-
-# If false, no module index is generated.
-# html_domain_indices = True
-
-# If false, no index is generated.
-# html_use_index = True
-
-# If true, the index is split into individual pages for each letter.
-# html_split_index = False
-
-# If true, links to the reST sources are added to the pages.
-# html_show_sourcelink = True
-
-# If true, "Created using Sphinx" is shown in the HTML footer. Default is True.
-# html_show_sphinx = True
-
-# If true, "(C) Copyright ..." is shown in the HTML footer. Default is True.
-# html_show_copyright = True
-
-# If true, an OpenSearch description file will be output, and all pages will
-# contain a <link> tag referring to it.  The value of this option must be the
-# base URL from which the finished HTML is served.
-# html_use_opensearch = ''
-
-# This is the file name suffix for HTML files (e.g. ".xhtml").
-# html_file_suffix = None
-
-# Language to be used for generating the HTML full-text search index.
-# Sphinx supports the following languages:
-#   'da', 'de', 'en', 'es', 'fi', 'fr', 'hu', 'it', 'ja'
-#   'nl', 'no', 'pt', 'ro', 'ru', 'sv', 'tr'
-# html_search_language = 'en'
-
-# A dictionary with options for the search language support, empty by default.
-# Now only 'ja' uses this config value
-# html_search_options = {'type': 'default'}
-
-# The name of a javascript file (relative to the configuration directory) that
-# implements a search results scorer. If empty, the default will be used.
-# html_search_scorer = 'scorer.js'
-
 # Output file base name for HTML help builder.
 htmlhelp_basename = "PyJWTdoc"
 
-# -- Options for LaTeX output ---------------------------------------------
-
-latex_elements = {
-    # The paper size ('letterpaper' or 'a4paper').
-    #'papersize': 'letterpaper',
-    # The font size ('10pt', '11pt' or '12pt').
-    #'pointsize': '10pt',
-    # Additional stuff for the LaTeX preamble.
-    #'preamble': '',
-    # Latex figure (float) alignment
-    #'figure_align': 'htbp',
-}
-
-# Grouping the document tree into LaTeX files. List of tuples
-# (source start file, target name, title,
-#  author, documentclass [howto, manual, or own class]).
-latex_documents = [
-    (master_doc, "PyJWT.tex", "PyJWT Documentation", "José Padilla", "manual")
-]
-
-# The name of an image file (relative to this directory) to place at the top of
-# the title page.
-# latex_logo = None
-
-# For "manual" documents, if this is true, then toplevel headings are parts,
-# not chapters.
-# latex_use_parts = False
-
-# If true, show page references after internal links.
-# latex_show_pagerefs = False
-
-# If true, show URL addresses after external links.
-# latex_show_urls = False
-
-# Documents to append as an appendix to all manuals.
-# latex_appendices = []
-
-# If false, no module index is generated.
-# latex_domain_indices = True
-
 
 # -- Options for manual page output ---------------------------------------
 
 # One entry per manual page. List of tuples
 # (source start file, name, description, authors, manual section).
-man_pages = [(master_doc, "pyjwt", "PyJWT Documentation", [author], 1)]
-
-# If true, show URL addresses after external links.
-# man_show_urls = False
+man_pages = [(master_doc, "pyjwt", u"PyJWT Documentation", [author], 1)]
 
 
 # -- Options for Texinfo output -------------------------------------------
@@ -282,22 +124,10 @@ def get_version(package):
     (
         master_doc,
         "PyJWT",
-        "PyJWT Documentation",
+        u"PyJWT Documentation",
         author,
         "PyJWT",
         "One line description of project.",
         "Miscellaneous",
     )
 ]
-
-# Documents to append as an appendix to all manuals.
-# texinfo_appendices = []
-
-# If false, no module index is generated.
-# texinfo_domain_indices = True
-
-# How to display URL addresses: 'footnote', 'no', or 'inline'.
-# texinfo_show_urls = 'footnote'
-
-# If true, do not generate a @detailmenu in the "Top" node's menu.
-# texinfo_no_detailmenu = False
diff --git a/pyproject.toml b/pyproject.toml
index 4efdeb32..49b360f2 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,3 +1,20 @@
+[build-system]
+requires = ["setuptools", "wheel"]
+build-backend = "setuptools.build_meta"
+
+
+[tool.coverage.run]
+parallel = true
+branch = true
+source = ["jwt"]
+
+[tool.coverage.paths]
+source = ["jwt", ".tox/*/site-packages"]
+
+[tool.coverage.report]
+show_missing = true
+
+
 [tool.black]
 line-length = 79
 
diff --git a/pytest.ini b/pytest.ini
deleted file mode 100644
index fb1850e4..00000000
--- a/pytest.ini
+++ /dev/null
@@ -1,2 +0,0 @@
-[tool:pytest]
-addopts = --cov-report term-missing --cov-config=.coveragerc --cov .
diff --git a/setup.cfg b/setup.cfg
index 6f6616b4..7981bfa7 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -37,11 +37,24 @@ console_scripts =
     pyjwt = jwt.__main__:main
 
 [options.extras_require]
+docs =
+    sphinx
+    sphinx-rtd-theme
+    zope.interface
 crypto =
-    cryptography >= 1.4
+    cryptography>=1.4
 tests =
-    pytest>=4.0.1,<5.0.0
-    pytest-cov>=2.6.0,<3.0.0
+    pytest>=6.0.0,<7.0.0
+    coverage[toml]==5.0.4
+dev =
+    sphinx
+    sphinx-rtd-theme
+    zope.interface
+    cryptography>=1.4
+    pytest>=6.0.0,<7.0.0
+    coverage[toml]==5.0.4
+    mypy
+    pre-commit
 
 [options.packages.find]
 exclude =
diff --git a/tests/utils.py b/tests/utils.py
index ad39f759..463deb06 100644
--- a/tests/utils.py
+++ b/tests/utils.py
@@ -29,7 +29,7 @@ def int_from_bytes(data, byteorder, signed=False):
         result = 0
 
         while len(data) > 0:
-            digit, = struct.unpack(">I", data[:4])
+            (digit,) = struct.unpack(">I", data[:4])
             result = (result << 32) + digit
             data = data[4:]
 
diff --git a/tox.ini b/tox.ini
index 8e14a535..159d7a63 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,27 +1,93 @@
+[pytest]
+strict = true
+addopts = -ra
+testpaths = tests
+filterwarnings =
+    once::Warning
+    ignore:::pympler[.*]
+
+
+[gh-actions]
+python =
+    3.6: py36
+    3.7: py37, docs
+    3.8: py38, lint, manifest, typing
+
+
+[gh-actions:env]
+PLATFORM =
+    ubuntu-latest: linux
+    windows-latest: windows
+
+
 [tox]
 envlist =
     lint
     typing
-    py{35,36,37,38}-crypto
-    py{35,36,37,38}-contrib_crypto
-    py{35,36,37,38}-nocrypto
+    py{36,37,38}-crypto-{linux,windows}
+    py{36,37,38}-nocrypto-{linux,windows}
+    manifest
+    docs
+    pypi-description
+    coverage-report
+isolated_build = True
 
 
 [testenv]
-extras = tests
-commands = pytest
-deps =
+# Prevent random setuptools/pip breakages like
+# https://github.com/pypa/setuptools/issues/1042 from breaking our builds.
+setenv =
+    VIRTUALENV_NO_DOWNLOAD=1
+extras =
+    tests
     crypto: cryptography
-    contrib_crypto: pycrypto
-    contrib_crypto: ecdsa
+commands = coverage run -m pytest {posargs}
+
+
+[testenv:docs]
+basepython = python3.7
+extras = docs
+commands =
+    sphinx-build -n -T -W -b html -d {envtmpdir}/doctrees docs docs/_build/html
+    sphinx-build -n -T -W -b doctest -d {envtmpdir}/doctrees docs docs/_build/html
+    python -m doctest README.rst
 
 
 [testenv:typing]
-deps = mypy
-commands = mypy --python-version 3.5 --ignore-missing-imports jwt
+basepython = python3.8
+extras = dev
+commands = mypy --ignore-missing-imports jwt
 
 
 [testenv:lint]
-deps = pre-commit
+basepython = python3.8
+extras = dev
 passenv = HOMEPATH  # needed on Windows
 commands = pre-commit run --all-files
+
+
+[testenv:manifest]
+basepython = python3.8
+deps = check-manifest
+skip_install = true
+commands = check-manifest
+
+
+[testenv:pypi-description]
+basepython = python3.8
+skip_install = true
+deps =
+    twine
+    pip >= 18.0.0
+commands =
+    pip wheel -w {envtmpdir}/build --no-deps .
+    twine check {envtmpdir}/build/*
+
+
+[testenv:coverage-report]
+basepython = python3.8
+skip_install = true
+deps = coverage[toml]==5.0.4
+commands =
+    coverage combine
+    coverage report