ESLint vs Ruff
Feature checklists rarely decide anything. What decides it is the pricing metric, who has to write the tests, and which limitation you can live with.
Entry price
Free and open source
Open sourceFree and open source
Open sourceWhat drives the bill
The metric that actually scales your invoice.
Free and open source. You pay in engineering time and CI minutes.
Free and open source. You pay in engineering time and CI minutes.
Free tier
Everything, self-hosted
Everything, self-hosted
Open source
MIT
MIT
Self-hostable
No-code authoring
Languages
Platforms
Fits teams
Adoption
Category standard
OpenJS Foundation · since 2013
Category standard
Astral · since 2022
Strengths
- The plugin ecosystem lets you enforce almost any convention as a rule.
- Autofix handles a large share of findings without human effort.
- Universal — every JavaScript tool integrates with it.
- Replaces Flake8, isort, Black, pyupgrade and more with a single fast binary.
- Fast enough to run on every keystroke in the editor.
- Straightforward migration from existing Flake8 configurations.
Limitations
- Configuration is a real project of its own, and the flat-config migration caused significant churn.
- Slow on large codebases without caching.
- Rule sprawl produces bikeshedding unless someone owns the config.
- Not every niche Flake8 plugin rule has been ported.
- Type checking is a separate concern — you still need mypy or ty.
- Rapid release cadence occasionally changes behaviour.
Best for
Every JavaScript and TypeScript project.
Every Python project.
All of these integrate with: VS Code, GitHub Actions.
Pricing last reviewed August 2026 and is indicative only — confirm on each vendor’s own page.