markuplint HTML Linter for All Markup Developers
markuplint is a comprehensive HTML linter designed for all markup developers. It enforces accessibility, spec compliance, and best practices across HTML, JSX, Vue, Svelte, Astro, PHP, Pug, and more template languages through a pluggable parser architecture.
npx skills add agentskillexchange/skills --skill markuplint-html-linter
markuplint is an open-source HTML linter built to help markup developers maintain high-quality, accessible, and standards-compliant HTML across modern web projects. Unlike generic linters that only check raw HTML, markuplint understands the output of template engines and component frameworks, making it uniquely suited for real-world codebases.
What this skill actually does
How It Works
markuplint operates as a Node.js CLI tool and can be integrated into CI/CD pipelines, editor workflows (via its official VS Code extension), or run standalone. It parses markup using framework-specific parser plugins — including @markuplint/jsx-parser, @markuplint/vue-parser, @markuplint/svelte-parser, @markuplint/astro-parser, @markuplint/php-parser, @markuplint/pug-parser, and more — then evaluates the parsed output against its rule set.
Key Features
- Multi-framework support: JSX, Vue, Svelte, Astro, Alpine.js, HTMX, Pug, PHP, Nunjucks, Mustache, Liquid, and EJS templates are all supported through dedicated parser plugins.
- Accessibility enforcement: Rules check for proper ARIA attributes, landmark roles, heading hierarchy, and semantic HTML usage to ensure WCAG compliance.
- HTML spec validation: Validates elements and attributes against the living HTML specification, catching deprecated patterns and invalid nesting.
- Custom rule configuration: Rules are fully configurable via .markuplintrc JSON or YAML config files, supporting per-file overrides and shared presets.
- VS Code integration: The official vscode-markuplint extension provides real-time linting feedback directly in the editor.
Integration Points
Install via npm with npm install -D markuplint or use npx for one-off runs. Configure rules in a .markuplintrc file at your project root. The CLI outputs standard lint results compatible with CI formatters. For monorepos, markuplint supports workspace-level configuration with per-package overrides.
Agent Integration
AI coding agents can use markuplint as a code quality gate — run it after generating or modifying HTML templates to catch accessibility violations, deprecated elements, or invalid attribute usage before committing. The structured JSON output format makes it easy to parse results programmatically and feed them back into the agent loop for auto-correction.