What it does
Black is an opinionated formatter for Python source code. It rewrites selected files to a consistent style, and its `--check` option reports whether formatting would change without writing files. The project includes configuration, editor, and continuous-integration guidance, making it possible to apply the same formatting rule locally and in review workflows.
Format first, then make the check repeatable
Install Black as a development tool and point it at one Python file or a source directory. The official usage guide documents black path/to/file.py to reformat in place and black --check path/to/file.py to test formatting without writing the file. The latter is a useful first CI check because it reports whether a contributor's changes would be reformatted.
Black deliberately makes many formatting choices for the project instead of exposing a long list of style switches. Its docs cover file discovery, configuration, editor integrations, a Docker image, and GitHub Actions. Teams should run it consistently and review large formatting-only diffs separately from behavior changes. Black targets Python, so it complements rather than replaces formatters for other languages.
Black is maintained in the Python Software Foundation's source repository and is distributed under the MIT License.
Strengths
- A single documented command formats files, while `--check` supports non-writing validation.
- The official docs describe configuration, editor integration, and CI use.
- The Python-focused scope gives teams a consistent formatter without a broad multi-language configuration.
Watch out for
- Black makes style decisions intentionally, so teams that need fine-grained formatting control may not prefer its defaults.
- Formatting changes should be separated from behavior changes when reviewing a large codebase.
Best for
- Python teams that want uniform formatting in developer workstations and CI.
- Maintainers seeking a formatter that requires fewer per-rule style decisions.
- Projects that want formatting checks to fail when files differ from Black's output.
Sources
- Black Documentation (Oct 25, 2026)
- The Basics | Black (Oct 25, 2026)
- Getting Started | Black (Oct 25, 2026)
- psf/black source repository (Oct 25, 2026)
- MIT License | Black Documentation (Oct 25, 2026)