How do I run ruff check without installing Ruff?

Use this online playground. It loads Ruff's official WebAssembly build in your browser, so pasting code is the same as running `ruff check` on the command line — same rules, same diagnostics — with no `pip install ruff` and no server round-trip. Edit the config in Settings to match your project's `pyproject.toml`.

Can I see the AST and tokens of my Python code?

Yes. Switch to the AST tab to see Ruff's parsed syntax tree, or the Tokens tab to see the raw token stream. The Formatter IR tab shows the intermediate representation Ruff's formatter builds. All three update live as you edit your code or settings.

Which Ruff version does this use, and does it upload my code?

It runs the official Ruff 0.16.2 WebAssembly build entirely in your browser — linting, formatting and parsing all happen locally, so your source code never leaves your machine. The Share feature encodes your code into the URL itself, so even sharing happens without a server.

How to Check Ruff Online — Live Ruff Playground

playground.pyloading Ruff…

import os, sys
from typing import List

def greet(names:List[str])->None:
    for n in names:
        msg = f'Hello, {n}!'
        print( msg )

greet(["world","ruff"])

168 chars | 9 lines

live

| Loading the Ruff engine…

Official Ruff 0.16.2 WebAssembly build — diagnostics, formatting, AST, tokens and the formatter IR run locally in your browser, nothing uploaded. Edit the settings, share a link to your snippet, updates live as you type.

How to Check Ruff Online: Live Ruff Playground (Lint, Format, AST)

Want to check Python with Ruff online without installing anything? Paste your code and this playground runs ruff check live — diagnostics, formatting, the AST, tokens and formatter IR all update as you type. It runs the official Ruff WebAssembly build entirely in your browser, so nothing is uploaded, and you can share a link that reopens your exact code and settings.

About Ruff Playground

This is a full, professional-grade playground for Ruff, the extremely fast Rust-based Python linter and formatter from Astral. It updates live as you type: pick a tab to see the lint diagnostics (ruff check), the formatted output (what ruff format would produce), the parsed AST, the raw token stream, the formatter's intermediate representation (IR), or the extracted comments. A light/dark theme toggle keeps the editor comfortable in any lighting.

**How to check Ruff online, step by step:** (1) Paste or type your Python into the editor — syntax highlighting and live linting start immediately. (2) Read the **Diagnostics** tab: each issue shows its rule code (e.g. F401 unused import, E701 multiple statements), line and column, and whether Ruff can auto-fix it. (3) Switch to **Formatted** to see the ruff format output, or **AST** / **Tokens** / **Formatter IR** to inspect how Ruff parses your code. (4) Open **Settings** to edit the Ruff config as JSON — the same fields you'd put under [tool.ruff] in pyproject.toml, including select, ignore, line-length and format.quote-style. (5) Hit **Share** to copy a link that reopens your exact code and settings.

Because it runs the official Ruff build compiled to WebAssembly (currently Ruff 0.16.2), everything happens locally in your browser — there is no server and your code is never uploaded. For a quick one-click lint or format without the extra views, use the simpler Ruff Linter & Formatter instead.

For a project-level decision, see our Ruff vs Pylint comparison tested on the same code. It shows which of 14 error categories each tool caught, what Ruff fixed automatically, measured CLI timings, and when Pylint's semantic and cross-file analysis still matters.

Frequently Asked Questions

Paste your Python into the editor above — it runs `ruff check` live in your browser and shows every diagnostic with its rule code, line and column, and whether it's auto-fixable. There's nothing to install and nothing is uploaded; it runs the official Ruff WebAssembly build locally. Switch tabs to also see the formatted output, AST, tokens and formatter IR.

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