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Ruff v0.16.0 now enables 413 rules by default, up from 59 in previous versions, dramatically increasing its default linting coverage.
Astral's Ruff v0.16.0 increased default rules from 59 to 413, catching syntax errors and runtime bugs that previously required explicit configuration. ✦ AI generated
Brent Westbrook · Simon Willison's Weblog · 2026-07-25 · original ↗
Ruff now enables 413 rules by default, up from 59 in previous versions. Since Ruff's default rule set was last modified in v0.1.0, the number of rules in Ruff has grown from 708 to 968. Many of these rules catch severe issues, including syntax errors and immediate runtime errors but were not previously enabled by default. With the new rule set, Ruff will bring these issues and many others to your attention without any Ruff configuration.
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- ·v0.16.0 enables 413 rules by default
- ·Up from just 59 in previous versions
- ·Default set unchanged since v0.1.0
- ·Syntax errors now flagged without config
- ·Immediate runtime errors caught by default
- ·Ruff's total rules grew from 708 to 968
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gives example → Running the latest Ruff against my three biggest projects — Datasette, sqlite-utils, and LLM — found hundreds of minor issues that breached the new default rules, and the upgrade was safe because all three projects have comprehensive test suites running against Python 3.10 through 3.14.Simon Willison · Simon Willison's Webloggives example → Running Ruff v0.16.0 against my three biggest Python projects found hundreds of minor issues, but comprehensive test suites made the upgrade safe.Brent Westbrook · Simon Willison's Weblogsupports → Running Ruff v0.16.0 against my three biggest Python projects found hundreds of minor issues, but comprehensive test suites made the upgrade safe.Brent Westbrook · Simon Willison's Weblogextends → Ruff now enables 413 rules by default, up from 59 in previous versions.Brent Westbrook · Simon Willison's Weblogexplains mechanism → Ruff's output provides everything a coding agent would need to fix the problems it identifies, enabling AI-assisted remediation.Brent Westbrook · Simon Willison's Weblogexplains mechanism → Many of the 968 rules that were not previously enabled by default catch severe issues including syntax errors and immediate runtime errors, and will now be brought to developers' attention without any Ruff configuration.Brent Westbrook · Simon Willison's Weblogsupports → Ruff's output provides everything a coding agent would need to fix the problems it identifies, enabling AI-assisted remediation.Brent Westbrook · Simon Willison's Weblogsupports → Given Astral's new home at OpenAI, Ruff's output format provides everything a coding agent would need to fix the problems.Simon Willison · Simon Willison's Weblog