Markuplint

Reference knowledge for working with Markuplint.

What is Markuplint

An HTML linter that checks conformance with HTML Standard, WAI-ARIA, and project-specific rules. Supports JSX, Vue, Svelte, Astro, Pug, PHP, and more via parser plugins.

• Official site: https://markuplint.dev
• GitHub: https://github.com/markuplint/markuplint
• Playground: https://playground.markuplint.dev

Documentation base URL: check the installed version with npx markuplint --version. If it contains alpha, beta, or rc, replace https://markuplint.dev with https://next.markuplint.dev in every documentation URL below — the stable site does not document prerelease behavior.

Reading Violation Messages

Format: message (ruleId) [named-rule]

The attribute name is duplicated (no-duplicate-attr) [html-standard/attr-duplication]

• ruleId (no-duplicate-attr) — the base rule. Always present.
• named-rule (html-standard/attr-duplication) — preset-defined alias. Present only for named rules. The namespace/ prefix indicates which preset defined it (e.g., a11y/, html-standard/, performance/).
• severity — error (exit code 1), warning (exit code 0 by default), or info.

To look up any rule: https://markuplint.dev/docs/rules/{ruleId}

CLI Quick Reference

# Basic lint
npx markuplint "src/**/*.html"

# JSON output (for programmatic use)
npx markuplint "src/**/*.html" --format JSON

# Auto-fix (rules that support it)
npx markuplint "src/**/*.html" --fix

# Preview fixes without writing
npx markuplint "src/**/*.html" --fix-dry-run

# Suppress current violations for gradual adoption
npx markuplint "src/**/*.html" --suppress

# Clean up fixed suppressions
npx markuplint "src/**/*.html" --prune-suppressions

# GitHub Actions annotations
npx markuplint "src/**/*.html" --format GitHub

# Limit output for large projects
npx markuplint "src/**/*.html" --max-count=50

Always quote glob patterns to prevent shell expansion.

Config Patterns

Disable a named rule

{ "rules": { "a11y/html-lang": false } }

Disable all rules in a namespace

{ "rules": { "a11y/*": false } }

Change severity

{ "rules": { "a11y/html-lang": "warning" } }

Element-specific rules

nodeRules — targets the matched element. childNodeRules — targets descendants (add "inheritance": true for all descendants, not just direct children).

Ancestor matching

Use :is(selector *). Do NOT use :closest() — it is deprecated.

{ "selector": "div:is(nav *)" }

Common Issues and Fixes

OGP / Open Graph property attribute

The property attribute is not in the HTML spec. See: https://markuplint.dev/docs/rules/no-unknown-attr#the-open-graph-protocol

no-unknown-attr with frameworks

Install the framework's spec plugin (e.g., @markuplint/react-spec). See: https://markuplint.dev/docs/guides/beyond-html#why-need-the-spec-plugins

no-unescaped-char false positives with template engines

Default mode only flags a literal <. The strict option (also flagging >, ", a bare &) can trigger false positives with some template syntaxes. Disable partially, turn off strict, or report: https://markuplint.dev/docs/rules/no-unescaped-char

--init is interactive only

npx markuplint --init requires terminal input. AI agents should write .markuplintrc directly.

Documentation URLs

Topic	URL
All rules	https://markuplint.dev/docs/rules
Specific rule	https://markuplint.dev/docs/rules/{rule-id}
Presets	https://markuplint.dev/docs/guides/presets
Framework setup	https://markuplint.dev/docs/guides/beyond-html
Config properties	https://markuplint.dev/docs/configuration/properties
Selectors	https://markuplint.dev/docs/guides/selectors
CLI options	https://markuplint.dev/docs/guides/cli
FAQ	https://markuplint.dev/docs/guides/faq
Migration (v4→v5)	https://markuplint.dev/docs/migration/v4-to-v5

Use WebFetch on these URLs when you need current details.