Black

Black is a Python formatter for developers and teams who want code style applied consistently rather than negotiated file by file. Its whole-file approach and broad editor and CI integrations make it a practical fit for shared workflows, provided you accept its fixed style and command-line orientation.

Overview

Black follows PEP 8 and reformats Python files in place, using a default line length of 88 characters. Its limited style options are the point: teams can reduce formatting debates and keep code visually consistent across projects. That trade-off is worthwhile when uniformity matters more than matching an existing indentation preference; Black offers no way to configure indentation style.

Black aims to keep code-review diffs small, and checks that the reformatted code has an effectively equivalent abstract syntax tree, raising an error if that check fails. Stable releases also preserve formatting across releases in the same calendar year when used with the same options, which can help avoid unnecessary style churn.

Key features

• Whole-file formatting: Black applies its format to complete files. This is a clear, repeatable policy for projects that want one standard, but it is not the choice for teams seeking a changed-lines-only workflow.
• Editor and CI integration: Documented integrations cover editors and IDEs such as PyCharm, IntelliJ IDEA, Vim, Neovim, Visual Studio Code, Sublime Text, and Emacs. GitHub Actions integration supports GitHub-hosted runner operating systems, making Black suitable for enforcing formatting in development and CI.
• Jupyter notebooks: Installing Black with the jupyter extra enables notebook formatting. It skips cells with automagics, non-Python or multiline magics, transformed magic code, or invalid syntax, so notebooks with those cells will not receive comprehensive formatting.
• Local and container workflows: The blackd HTTP server binds to localhost by default, and official Docker images have release and prerelease tags. Black installs with pip and requires Python 3.10 or newer to run.
• Python compatibility: Black promises support for Python versions that have not reached end of life, both for running the formatter and formatting code.

Black is fundamentally a command-line tool and does not provide a Python interface. That is a meaningful constraint for developers who want to embed it as a library, even though integrations can bring it into editors and automation.

Pricing

Black is free: the Black plan costs nothing and provides an MIT-licensed Python code formatter. There is no free trial because the software is already available at no cost, and no paid tier or seat-based pricing is part of this offer. The practical cost is accepting its fixed formatting policy and installing it in an environment with Python 3.10 or newer.

Platforms

Black supports Windows, macOS, and Linux, as well as self-hosted use. Its local HTTP server adds an API-style workflow, but does not change the core product's command-line nature or provide a Python library API. The MIT license allows the formatter to fit into open-source and commercial development workflows.

Who it's for

Black is best for Python developers and teams that want a shared, low-debate formatting standard across editors, notebooks, and CI. The syntax-equivalence check and stable-release behavior strengthen its appeal for teams that value predictable automated formatting. Look elsewhere if your project requires configurable indentation, a Python interface, or notebook formatting that handles magic-heavy cells.

Pros and cons

Pros

• Consistent team style: Few formatting choices make it easier to apply the same conventions across projects.
• Safety check: AST equivalence checking can catch a formatting result that does not preserve the code's structure.
• Broad workflow coverage: Editor, GitHub Actions, notebook, Docker, and local-server options support use beyond a standalone terminal command.
• Free and permissively licensed: The MIT license and 0.00 USD price make it accessible without a paid plan.

Cons

• Fixed indentation: No indentation-style setting rules out teams that must follow a different house convention.
• No Python library API: Black cannot be used as a Python interface for embedding directly in another program.
• Notebook edge cases: Certain magic commands, transformed code, and invalid syntax cause cells to be skipped.
• Runtime requirement: Running Black requires Python 3.10 or newer.

Alternatives

For other options, browse Code Formatting Tools. Choose Ruff if you want a free Python-ecosystem alternative from a maker focused on high-performance developer tools. rustfmt is a free alternative for readers whose code is in Rust, while Prettier is a free open-source formatter for a different set of platforms, including web and extension use.

Scalafmt is the free option for Scala formatting; Taplo is another free choice with API and extension platforms. For web projects, Biome offers an open-source toolchain. CSharpier suits C# and XML formatting as a .NET tool. Accessibility Test Framework for Android is a free Android accessibility-testing alternative, rather than a Python formatter.

Verdict

Choose Black when your Python project needs consistent formatting across developers and automation, and you are willing to accept its fixed style. The free MIT-licensed tool, AST safety check, and editor and CI integrations make that policy easy to carry through a workflow. Choose another tool if configurable indentation or a Python library interface is essential.