Ruff v0.16.0: Default Rule Set Jumps From 59 to 413

Source: Astral — 2026-07-23

Summary

Astral shipped Ruff v0.16.0, a major release for the Python linter/formatter that expands the default-enabled rule set from 59 rules to 413 (while removing 18 opinionated pycodestyle/pyflakes rules like E402, E711-E714, and F403). The release also adds ruff: ignore suppression comments mirroring noqa syntax, default formatting of Python code blocks embedded in Markdown files, and diff-based diagnostics for both check and format --check, including GitHub/GitLab CI output formats.

Key Takeaways

• Default-enabled rules jump roughly 7x, from 59 to 413, meaning most existing projects will surface many new diagnostics on upgrade without any config changes; Astral removed 18 more opinionated rules (E401, E402, E701-E703, E711-E714, E721, E731, E741-E743, F403, F405-F406, F722) as part of the rebalance.
• New ruff: ignore suppression comments work like noqa but with Ruff's own syntax, usable at the end of a line or on the line preceding a diagnostic (e.g. import math # ruff: ignore[F401]).
• The formatter now reformats Python code blocks embedded in Markdown files by default (recognizing python, py, python3, py3, pyi, and pycon info strings), with pyi blocks formatted as stub files and pycon blocks as REPL sessions; teams that don't want this can exclude *.md via extend-exclude.
• Both ruff check and ruff format --check now show diffs of proposed changes directly in the CLI output, and format --check gained github and gitlab output formats for CI integration.
• JSON output now allows null for fields like filename, location, and end_location instead of defaulting to empty strings, and 12 previously preview rules stabilized, including CPY001 (copyright notice checks) and RUF036 (union type ordering).

Discussion

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