diff --git a/MANIFEST.in b/MANIFEST.in
index a98d169..3492f72 100644
--- a/MANIFEST.in
+++ b/MANIFEST.in
@@ -10,6 +10,6 @@ exclude tasks.py
 exclude tests/test_fixtures/*/*.json
 exclude tests/test_hpack_integration.py
 
-include README.rst LICENSE CHANGELOG.rst CONTRIBUTORS.rst pyproject.toml tox.ini
+include README.rst LICENSE CHANGELOG.rst CONTRIBUTORS.rst pyproject.toml
 
 global-exclude *.pyc *.pyo *.swo *.swp *.map *.yml *.DS_Store
diff --git a/pyproject.toml b/pyproject.toml
index 470e9a1..db11975 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -7,7 +7,7 @@ build-backend = "setuptools.build_meta"
 
 [project]
 name = "hpack"
-description = "Pure-Python HPACK header compression"
+description = "Pure-Python HPACK header encoding"
 readme = { file = "README.rst", content-type = "text/x-rst" }
 license = { file = "LICENSE" }
 
@@ -46,6 +46,12 @@ classifiers = [
 "Documentation" = "https://python-hyper.org/"
 
 [dependency-groups]
+dev = [
+  { include-group = "testing" },
+  { include-group = "linting" },
+  { include-group = "packaging" },
+  { include-group = "docs" },
+]
 testing = [
   "pytest>=8.3.3,<9",
   "pytest-cov>=6.0.0,<7",
@@ -103,3 +109,83 @@ source = [
   "src/",
   ".tox/**/site-packages/",
 ]
+
+[tool.tox]
+min_version = "4.23.2"
+env_list = [ "py39", "py310", "py311", "py312", "py313", "pypy3", "lint", "docs", "packaging" ]
+
+[tool.tox.gh-actions]
+python = """
+  3.9: py39, h2spec, lint, docs, packaging
+  3.10: py310
+  3.11: py311
+  3.12: py312
+  3.13: py313
+  pypy3: pypy3
+"""
+
+[tool.tox.env_run_base]
+pass_env = [
+  "GITHUB_*",
+]
+dependency_groups = ["testing"]
+commands = [
+  ["pytest", "--cov-report=xml", "--cov-report=term", "--cov=hpack", { replace = "posargs", extend = true }]
+]
+
+[tool.tox.env.pypy3]
+# temporarily disable coverage testing on PyPy due to performance problems
+commands = [
+  ["pytest", { replace = "posargs", extend = true }]
+]
+
+[tool.tox.env.lint]
+dependency_groups = ["linting"]
+commands = [
+  ["ruff", "check", "src/"],
+  ["mypy", "src/"],
+]
+
+[tool.tox.env.docs]
+dependency_groups = ["docs"]
+allowlist_externals = ["make"]
+changedir = "{toxinidir}/docs"
+commands = [
+  ["make", "clean"],
+  ["make", "html"],
+]
+
+[tool.tox.env.packaging]
+base_python = ["python39"]
+dependency_groups = ["packaging"]
+allowlist_externals = ["rm"]
+commands = [
+  ["rm", "-rf", "dist/"],
+  ["check-manifest"],
+  ["python", "-m", "build", "--outdir", "dist/"],
+  ["twine", "check", "dist/*"],
+]
+
+[tool.tox.env.publish]
+base_python = "{[tool.tox.env.packaging]base_python}"
+deps = "{[tool.tox.env.packaging]deps}"
+allowlist_externals = "{[tool.tox.env.packaging]allowlist_externals}"
+commands = [
+    "{[testenv:packaging]commands}",
+    ["twine", "upload", "dist/*"],
+]
+
+[tool.tox.env.bench]
+deps = [
+  "{[tool.tox.env]deps}",
+  "pytest-benchmark==3.2.3",
+]
+commands = [
+  ["pytest {toxinidir}/bench/ --benchmark-only --benchmark-group-by=name --benchmark-autosave --benchmark-compare --benchmark-min-rounds=500000"],
+]
+
+[tool.tox.env.create_test_output]
+base_python = ["python3.9"]
+commands = [
+  ["python", "{toxinidir}/utils/create_test_output.py", { replace = "posargs", extend = true }],
+]
diff --git a/tox.ini b/tox.ini
deleted file mode 100644
index 75e5c44..0000000
--- a/tox.ini
+++ /dev/null
@@ -1,71 +0,0 @@
-[tox]
-envlist = py39, py310, py311, py312, py313, pypy3, lint, docs, packaging
-
-[gh-actions]
-python =
-    3.9: py39, lint, docs, packaging
-    3.10: py310
-    3.11: py311
-    3.12: py312
-    3.13: py313
-    pypy3: pypy3
-
-[testenv]
-passenv =
-    GITHUB_*
-dependency_groups = testing
-commands =
-    pytest --cov-report=xml  --cov-report=term --cov=hpack {posargs}
-
-[testenv:pypy3]
-# temporarily disable coverage testing on PyPy due to performance problems
-commands = pytest {posargs}
-
-[testenv:lint]
-dependency_groups = linting
-allowlist_externals =
-    ruff
-    mypy
-commands =
-    ruff check src/ tests/
-    mypy --strict src/
-
-[testenv:docs]
-dependency_groups = docs
-allowlist_externals = make
-changedir = {toxinidir}/docs
-commands =
-    make clean
-    make html
-
-[testenv:packaging]
-basepython = python3.9
-dependency_groups = packaging
-allowlist_externals = rm
-commands =
-    rm -rf dist/
-    check-manifest
-    python -m build --outdir dist/
-    twine check dist/*
-
-[testenv:publish]
-basepython = {[testenv:packaging]basepython}
-deps =
-    {[testenv:packaging]deps}
-allowlist_externals = {[testenv:packaging]allowlist_externals}
-commands =
-    {[testenv:packaging]commands}
-    twine upload dist/*
-
-[testenv:bench]
-deps =
-    {[testenv]deps}
-    pytest-benchmark==3.2.3
-commands =
-    pytest {toxinidir}/bench/ --benchmark-only --benchmark-group-by=name --benchmark-autosave --benchmark-compare --benchmark-min-rounds=500000
-
-[testenv:create_test_output]
-basepython = python3.9
-; rm -rf hpack-test-case/
-; git clone https://github.com/http2jp/hpack-test-case.git
-commands = python {toxinidir}/utils/create_test_output.py {posargs}