# Python formatter

> Format Python code in the Black style with Ruff, running in your browser via WebAssembly. Choose line length and quotes. Free, nothing is uploaded.

Canonical: https://toolspace.tech/python-formatter/
Last updated: 2026-10-25

Format Python in the Black style with Ruff’s formatter, compiled to WebAssembly and running in your browser. Choose line length, quotes and indentation; syntax errors are shown with their line.

This is an interactive tool that runs in the browser: [open the Python formatter](https://toolspace.tech/python-formatter/) to use it. Nothing typed into it is uploaded.

## Common mistakes

### Pasting from an interactive session

Lines starting with >>> or In [1]: aren’t Python. Remove the prompts and the printed output first.

### Mixing tabs and spaces

Python rejects indentation that mixes the two inconsistently, so the formatter reports it as an error. Re-indent the block, then format.

### Being surprised by the magic trailing comma

A comma after the last item keeps a call, list or dict split one item per line. Remove the comma if you want it joined onto one line.

### Expecting a linter

Unused imports, undefined names and bugs pass through untouched. Formatting only changes layout.

## How it works

1. **Paste Python:** A function, a script or a module. Open or drop a .py file; nothing is uploaded.
2. **Choose the options:** “Default” is 4 spaces, as PEP 8 recommends. Set the line length (80, 100 or 120; Black’s own default is 88) and single or double quotes.
3. **Read any error:** Code that doesn’t parse isn’t formatted: you get the error and a button that jumps to its line.

## Questions

### Is this the same as Black?

Ruff’s formatter is built as a drop-in replacement for Black and gives the same output on almost all code. The few differences are documented by the Ruff project and rarely show up in everyday code.

### Does it sort imports or fix lint errors?

No. It only formats. Sorting imports and fixing lint findings are separate Ruff commands (ruff check --fix) that don’t run here.

### Why is a line still longer than the limit?

Like Black, Ruff doesn’t split long strings or comments, and a single long name can’t be broken. Those lines stay over the limit.

### Which Python syntax is supported?

Current Python 3: type hints, f-strings, async and await, decorators, dataclasses, match statements and the walrus operator.

## Related

- [Code beautifier](https://toolspace.tech/code-beautifier/)
- [SQL formatter](https://toolspace.tech/sql-formatter/)
- [JSON formatter](https://toolspace.tech/json-formatter/)
- [Regex tester](https://toolspace.tech/regex-tester/)