# Ruff Formatter
The Ruff formatter is an extremely fast Python code formatter that ships as part of the `ruff`
CLI.
## Goals
The formatter is designed to be a drop-in replacement for [Black](https://github.com/psf/black),
but with an excessive focus on performance and direct integration with Ruff.
Specifically, the formatter is intended to emit near-identical output when run over Black-formatted
code. When run over extensive Black-formatted projects like Django and Zulip, > 99.9% of lines
are formatted identically. When migrating an existing project from Black to Ruff, you should expect
to see a few differences on the margins, but the vast majority of your code should be unchanged.
If you identify deviations in your project, spot-check them against the [intentional deviations](https://docs.astral.sh/ruff/formatter/black/)
enumerated below, as well as the [unintentional deviations](https://github.com/astral-sh/ruff/issues?q=is%3Aopen+is%3Aissue+label%3Aformatter)
filed in the issue tracker. If you've identified a new deviation, please [file an issue](https://github.com/astral-sh/ruff/issues/new).
When run over _non_-Black-formatted code, the formatter makes some different decisions than Black,
and so more deviations should be expected, especially around the treatment of end-of-line comments.
For details, see [Style Guide](https://docs.astral.sh/ruff/formatter/#style-guide).
## Getting started
Head to [The Ruff Formatter](https://docs.astral.sh/ruff/formatter/) for usage instructions and a comparison to Black.
## Versioning
This crate is an internal component of [Ruff](https://crates.io/crates/ruff). The Rust API exposed
here is unstable and will have frequent breaking changes.
This version (0.0.6) is a component of [Ruff 0.16.0](https://crates.io/crates/ruff/0.16.0). The
source can be found [here](https://github.com/astral-sh/ruff/blob/0.16.0/crates/ruff_python_formatter).
See Ruff's [crate versioning policy](https://docs.astral.sh/ruff/versioning/#crate-versioning) for
details on versioning.
