How to format Python code online
- Paste your Python code into the left panel, or click Sample to try it.
- Pick a line length. 88 is Black's default; 79 matches strict PEP 8.
- Click Format code and copy the result from the right panel.
Formatting never changes what your code does. Black checks that the formatted code compiles to the same program as your original before returning it.
What Black changes
- Indentation: always 4 spaces, never tabs
- Spacing: one space around operators and after commas, none inside brackets
- Long lines: split across lines, with one item per line when they still don't fit
- Blank lines: two between top-level functions and classes, one between methods
- Quotes: double quotes by default (you can turn this off)
- Trailing commas: added to exploded lists, so future diffs only touch one line
Why use a formatter?
A formatter ends style debates in code review: everyone's code comes out the same, so reviewers can focus on what it does. It's also a quick way to tidy AI-generated code or snippets copied from different sources before you commit them. To format a whole project, install Black with pip install black and run black . — this page uses the same rules.
Related guides
- How to Format Python Code (Black, Online & in VS Code)
- Black vs autopep8 vs YAPF vs Ruff: Which Python Formatter Should You Use?
Frequently asked questions
What formatter does this use?
Black, the most widely used Python formatter (version 24.10). Running it here gives the same output as running black on your machine with the same settings.
Which line length should I pick?
88 is Black's default and what most projects use. Choose 79 for strict PEP 8, or 100 / 120 if your team prefers wider lines.
What does “Normalize quotes” do?
Black turns 'single' quotes into "double" quotes unless that would add escapes. Untick it to keep your quotes as they are, like black --skip-string-normalization.
Why do I get “Could not parse your code”?
Black only formats valid Python 3. The message gives the line and column of the syntax error. Fix it and try again; failed attempts do not use up a free try.
Do I need an account?
No — you can use the free tools 5 times without one. After that, sign up or log in (it is free) for unlimited use of every tool.
Is my code stored?
No. Your code is processed in memory to produce the result and is never saved. See our Privacy Policy.