Ruff v0.16.0 enables 413 default linting rules, up from 59

Astral released Ruff v0.16.0 on July 23, 2026, increasing the number of rules enabled by default from 59 to 413. The total rule set grew from 708 to 968 since the last modification to the default set in v0.1.0.

Many newly enabled rules detect severe issues such as syntax errors and immediate runtime errors, which were previously only available as opt-in checks. With this change, Ruff surfaces these issues without requiring any user configuration.

A one-liner command can run the new checks on any Python project: uvx ruff@latest check .

The author tested the update on three projects—Datasette, sqlite-utils, and LLM—finding hundreds of issues that breached the new default rules. Automated fixes resolved the bulk of the problems; for sqlite-utils, the command reported 1,618 errors, fixing 1,538 and leaving 80 remaining.

Examples of newly flagged issues include using datetime.datetime.now() without a timezone argument, catching a blind Exception, and accessing attributes without assignment. Ruff provides detailed explanations and suggested fixes for each issue.