Stylelint
CSS linter. PostCSS-based. 170+ built-in rules + plugin ecosystem. Supports CSS, SCSS, Less, Sugar SS. Standard for CSS codebases since ~2016. Equivalent to ESLint for JS.
Rules: no-duplicate-selectors, color-hex-length, declaration-block-trailing-semicolon. Auto-fix for many rules. Editor integration via stylelint-language-server. Tailwind class ordering, BEM validation, accessibility checks via plugins. Modern alternative: Biome adds CSS linting (early stage), threatens Stylelint eventually. Pre-Stylelint: CSSLint (deprecated), scss-lint (Ruby-based, slow). Stylelint v16 (2024) ESM-native. Standard setup: stylelint-config-standard + custom rules override for team conventions.