What Python formatting rules does this tool apply?

The formatter normalizes indentation to 4 spaces (PEP 8 standard), removes trailing whitespace from all lines, adds blank lines before def and class declarations, collapses more than two consecutive blank lines, and adds spaces around assignment operators.

Does this tool run on a server?

No. All formatting logic runs entirely in your browser using JavaScript. Your code is never sent to any server, making it safe for proprietary or sensitive code.

Is this equivalent to Black or autopep8?

This tool covers the most common PEP 8 fixes: indentation, blank lines, and operator spacing. For full compliance with all PEP 8 rules, use Black or autopep8 in your local environment. This tool is ideal for quick fixes without needing a Python installation.

Can I format Jupyter notebook cells?

Yes. Paste the cell contents into the Input panel, format, and copy the result back. The formatter handles any valid Python code fragment, not just complete scripts.

PEP 8 is the official Python style guide. It specifies conventions for indentation (4 spaces), line length, blank lines between functions and classes, whitespace around operators, and more. Following PEP 8 makes Python code easier to read and maintain.

Why does my code look different after formatting?

The formatter corrects any non-standard indentation, removes extra blank lines, and adds required spacing. These changes follow PEP 8 conventions and make the code more consistent, even if it was previously working without them.

Does the formatter handle class definitions and decorators?

Yes. The formatter ensures blank lines before class and def keywords, and preserves decorator lines. Nested classes and methods are re-indented correctly based on their block depth.

What happens if I paste invalid Python syntax?

The formatter applies rule-based transformations without parsing the AST, so it will still process the code and apply whitespace and indentation fixes. It does not validate syntax or raise errors for invalid Python.

Can I use this to prepare code for AI tools like ChatGPT or Copilot?

Absolutely. Consistently formatted code produces better results from AI coding assistants and code review tools. Paste your code here first to clean it up before sending it to an LLM.

Python Formatter

Format Python code with PEP 8 rules: fix indentation, blank lines, operator spacing, and trailing whitespace: no server required.

Input10 lines

Output

What gets fixed

• Indentation normalized to 4 spaces (PEP 8)
• Trailing whitespace removed from all lines
• Blank lines before def / class declarations
• Consecutive blank lines collapsed to maximum 2
• Spacing around assignment operators

Free online Python code formatter that fixes indentation and PEP 8 style instantly

Poorly formatted Python is harder to read, harder to debug, and likely to fail code reviews. The Python Formatter on AlteredIdea applies the most common PEP 8 corrections: indentation normalization to 4 spaces, trailing whitespace removal, blank lines before function and class definitions, and spacing around operators: all without leaving your browser or installing any tools.

This formatter is especially useful for developers working with pasted code from Stack Overflow, generated output from AI tools, or legacy scripts with inconsistent indentation. It also works well as a pre-processor before submitting code to ChatGPT, GitHub Copilot, or other AI coding assistants, where clean formatting leads to more accurate suggestions and completions.

Step-by-step guide

1
Paste your Python code
Copy any Python snippet, function, class, or script and paste it into the Input panel on the left.
2
Click Format Code
Hit the Format Code button to apply PEP 8 formatting rules instantly. No server round-trip: all processing happens in your browser.
3
Review the formatted output
The Output panel shows your reformatted code. A character difference indicator tells you how much was cleaned up.
4
Copy the result
Click Copy Output to copy the formatted code to your clipboard, ready to paste back into your editor or notebook.
5
Clear and repeat
Use the Clear button to reset both panels and format another snippet. The formatter handles multiple passes safely.

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Frequently Asked Questions

What Python formatting rules does this tool apply?: The formatter normalizes indentation to 4 spaces (PEP 8 standard), removes trailing whitespace from all lines, adds blank lines before def and class declarations, collapses more than two consecutive blank lines, and adds spaces around assignment operators.
Does this tool run on a server?: No. All formatting logic runs entirely in your browser using JavaScript. Your code is never sent to any server, making it safe for proprietary or sensitive code.
Is this equivalent to Black or autopep8?: This tool covers the most common PEP 8 fixes: indentation, blank lines, and operator spacing. For full compliance with all PEP 8 rules, use Black or autopep8 in your local environment. This tool is ideal for quick fixes without needing a Python installation.
Can I format Jupyter notebook cells?: Yes. Paste the cell contents into the Input panel, format, and copy the result back. The formatter handles any valid Python code fragment, not just complete scripts.
What is PEP 8?: PEP 8 is the official Python style guide. It specifies conventions for indentation (4 spaces), line length, blank lines between functions and classes, whitespace around operators, and more. Following PEP 8 makes Python code easier to read and maintain.
Why does my code look different after formatting?: The formatter corrects any non-standard indentation, removes extra blank lines, and adds required spacing. These changes follow PEP 8 conventions and make the code more consistent, even if it was previously working without them.
Does the formatter handle class definitions and decorators?: Yes. The formatter ensures blank lines before class and def keywords, and preserves decorator lines. Nested classes and methods are re-indented correctly based on their block depth.
What happens if I paste invalid Python syntax?: The formatter applies rule-based transformations without parsing the AST, so it will still process the code and apply whitespace and indentation fixes. It does not validate syntax or raise errors for invalid Python.
Can I use this to prepare code for AI tools like ChatGPT or Copilot?: Absolutely. Consistently formatted code produces better results from AI coding assistants and code review tools. Paste your code here first to clean it up before sending it to an LLM.

AlteredIdea vs alternatives

vs Black / autopep8: Those tools require a Python environment and command-line access. AlteredIdea works instantly in any browser, on any device, with no setup.

vs browser extensions: No install, no permissions, works on any device.

vs paid tools: Completely free, no account required.

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