Ruff vs SonarQube

Free and open source

From €32 per year per 100k lines of code (Developer Edition, indicative)

Free and open source. You pay in engineering time and CI minutes.

Licensed by lines of code, which makes cost predictable but expensive on large monorepos. Branch and PR analysis requires a paid edition.

Everything, self-hosted

Community Build is free and self-hosted, covering the main languages without branch analysis.

Category standard

Astral · since 2022

Category standard

Sonar · since 2007

• 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.

• Clean-as-you-code is the only quality-gate model that reliably works on legacy codebases.
• Very broad language coverage from one tool and one gate.
• Self-hosting satisfies organisations that cannot send source code externally.

• 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.

• Branch and pull-request analysis — the feature most teams actually need — is paid only.
• Default rule sets are noisy until tuned to the team.
• Self-hosted instances need real resources and maintenance.

Every Python project.

Polyglot organisations that need one quality gate across every repository.