Ruff

An extremely fast Python linter and code formatter, written in Rust.

Linting the CPython codebase from scratch.

⚡️ 10-100x faster than existing linters (like Flake8) and formatters (like Black)
Installable via pip
️ pyproject.toml support
Python 3.13 compatibility
⚖️ Drop-in parity with Flake8, isort, and Black
Built-in caching, to avoid re-analyzing unchanged files
Fix support, for automatic error correction (e.g., automatically remove unused imports)
Over 800 built-in rules, with native re-implementations
of popular Flake8 plugins, like flake8-bugbear
⌨️ First-party editor integrations for
VS Code and more
Monorepo-friendly, with hierarchical and cascading configuration

Ruff aims to be orders of magnitude faster than alternative tools while integrating more
functionality behind a single, common interface.

Ruff can be used to replace Flake8 (plus dozens of plugins),
Black, isort,
pydocstyle, pyupgrade,
autoflake, and more, all while executing tens or hundreds of
times faster than any individual tool.

Ruff is extremely actively developed and used in major open-source projects like:

...and many more.

Ruff is backed by Astral. Read the launch post,
or the original project announcement.

Testimonials

Sebastián Ramírez, creator
of FastAPI:

Ruff is so fast that sometimes I add an intentional bug in the code just to confirm it's actually
running and checking the code.

Nick Schrock, founder of Elementl,
co-creator of GraphQL:

Why is Ruff a gamechanger? Primarily because it is nearly 1000x faster. Literally. Not a typo. On
our largest module (dagster itself, 250k LOC) pylint takes about 2.5 minutes, parallelized across 4
cores on my M1. Running ruff against our entire codebase takes .4 seconds.

Bryan Van de Ven, co-creator
of Bokeh, original author
of Conda:

Ruff is ~150-200x faster than flake8 on my machine, scanning the whole repo takes ~0.2s instead of
~20s. This is an enormous quality of life improvement for local dev. It's fast enough that I added
it as an actual commit hook, which is terrific.

Timothy Crosley,
creator of isort:

Just switched my first project to Ruff. Only one downside so far: it's so fast I couldn't believe
it was working till I intentionally introduced some errors.

Tim Abbott, lead
developer of Zulip:

This is just ridiculously fast... ruff is amazing.

Getting Started

For more, see the documentation.

Installation

Ruff is available as ruff on PyPI:

Starting with version 0.5.0, Ruff can be installed with our standalone installers:

You can also install Ruff via Homebrew, Conda,
and with a variety of other package managers.

Usage

To run Ruff as a linter, try any of the following:

Or, to run Ruff as a formatter:

Ruff can also be used as a pre-commit hook via ruff-pre-commit:

Ruff can also be used as a VS Code extension or with various other editors.

Ruff can also be used as a GitHub Action via
ruff-action:

Configuration

Ruff can be configured through a pyproject.toml, ruff.toml, or .ruff.toml file (see:
Configuration, or Settings
for a complete list of all configuration options).

If left unspecified, Ruff's default configuration is equivalent to the following ruff.toml file:

Note that, in a pyproject.toml, each section header should be prefixed with tool.ruff. For
example, [lint] should be replaced with [tool.ruff.lint].

Some configuration options can be provided via dedicated command-line arguments, such as those
related to rule enablement and disablement, file discovery, and logging level:

The remaining configuration options can be provided through a catch-all --config argument:

To opt in to the latest lint rules, formatter style changes, interface updates, and more, enable
preview mode by setting preview = true in your configuration
file or passing --preview on the command line. Preview mode enables a collection of unstable
features that may change prior to stabilization.

See ruff help for more on Ruff's top-level commands, or ruff help check and ruff help format
for more on the linting and formatting commands, respectively.

Rules

Ruff supports over 800 lint rules, many of which are inspired by popular tools like Flake8,
isort, pyupgrade, and others. Regardless of the rule's origin, Ruff re-implements every rule in
Rust as a first-party feature.

By default, Ruff enables Flake8's F rules, along with a subset of the E rules, omitting any
stylistic rules that overlap with the use of a formatter, like ruff format or
Black.

If you're just getting started with Ruff, the default rule set is a great place to start: it
catches a wide variety of common errors (like unused imports) with zero configuration.

Beyond the defaults, Ruff re-implements some of the most popular Flake8 plugins and related code
quality tools, including:

For a complete enumeration of the supported rules, see Rules.

Contributing

Contributions are welcome and highly appreciated. To get started, check out the
contributing guidelines.

You can also join us on Discord.

Support

Having trouble? Check out the existing issues on GitHub,
or feel free to open a new one.

You can also ask for help on Discord.

Acknowledgements

Ruff's linter draws on both the APIs and implementation details of many other
tools in the Python ecosystem, especially Flake8, Pyflakes,
pycodestyle, pydocstyle,
pyupgrade, and isort.

In some cases, Ruff includes a "direct" Rust port of the corresponding tool.
We're grateful to the maintainers of these tools for their work, and for all
the value they've provided to the Python community.

Ruff's formatter is built on a fork of Rome's rome_formatter,
and again draws on both API and implementation details from Rome,
Prettier, and Black.

Ruff's import resolver is based on the import resolution algorithm from Pyright.

Ruff is also influenced by a number of tools outside the Python ecosystem, like
Clippy and ESLint.

Ruff is the beneficiary of a large number of contributors.

Ruff is released under the MIT license.