markdown-it
Highly accurate and extensible Markdown parser for JavaScript. markdown-it follows the CommonMark spec, supports GFM extensions (tables, strikethrough, task lists via plugins), and has a rich plugin ecosystem for custom syntax extensions. Outputs sanitized HTML. Used in documentation sites, chat applications, and any JavaScript application needing Markdown-to-HTML conversion.
Score Breakdown
⚙ Agent Friendliness
🔒 Security
XSS-safe by default (html: false). Always add DOMPurify for user-generated Markdown. linkify blocks javascript: protocol. Well-audited codebase with active security fixes.
⚡ Reliability
Best When
You need fast, spec-compliant Markdown to HTML conversion in JavaScript with extensibility for custom syntax and reliable XSS-safe output.
Avoid When
You need document format conversion beyond HTML output or WYSIWYG editing features.
Use Cases
- • Convert agent-generated Markdown content to HTML for display in web interfaces without security risk using built-in HTML sanitization
- • Build Markdown-powered documentation systems for agent tools where authors write Markdown and the tool renders HTML
- • Add custom syntax extensions to agent Markdown processing using markdown-it plugins — math equations, diagrams, custom blocks
- • Process user-submitted Markdown in agent chat interfaces and notebooks with XSS-safe HTML output
- • Generate HTML email content from Markdown templates in agent notification pipelines for readable source and safe rendered output
Not For
- • Pandoc-level document conversion (Word, PDF, LaTeX) — use Pandoc for multi-format document conversion; markdown-it outputs HTML only
- • WYSIWYG editor backends — use ProseMirror or TipTap for rich text editors; markdown-it is a parser, not an editor
- • Processing untrusted Markdown with HTML allowed — disable html option and use DOMPurify for extra sanitization with user-generated content
Interface
Authentication
No authentication — local Markdown parsing library.
Pricing
markdown-it is open source and free.
Agent Metadata
Known Gotchas
- ⚠ HTML in Markdown is disabled by default (html: false option) — inline HTML tags are escaped; enable html: true only for trusted content authors, not user input
- ⚠ XSS via Markdown is still possible even with html: false — javascript: protocol in links is blocked by linkify, but always run output through DOMPurify for untrusted user content
- ⚠ GFM features (tables, task lists, strikethrough) require plugins — markdown-it-task-lists, @vscode/markdown-it-katex etc.; CommonMark tables need markdown-it-table
- ⚠ Plugin load order matters — plugins that modify the rendering pipeline must be loaded in the correct order; conflicting plugins can produce garbled output
- ⚠ markdown-it doesn't handle front matter (---YAML---) — use gray-matter separately to strip front matter before passing to markdown-it
- ⚠ Syntax highlighting in code blocks requires a plugin (highlight.js or shiki integration) — default code blocks output plain <code> without language classes
Alternatives
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Scores are editorial opinions as of 2026-03-07.