Render a heading
Input
# HelloExample output
<h1>Hello</h1>
Markdown Preview
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About this tool, examples & FAQ
Preview Markdown visually and copy allowlist-sanitized HTML with GitHub-flavored syntax and optional hard line breaks.
Key facts
| Output | Sanitized HTML markup |
|---|---|
| Visual preview | Sandboxed, non-interactive, and blocked from network requests |
| Processing | Local Web Worker; Markdown is not uploaded |
| Maximum input | 1 MB |
How to use
- Paste Markdown into the input editor.
- Choose GitHub-flavored syntax and line-break behavior.
- Run the tool to see a sandboxed visual preview and the generated HTML source.
- Review the result, then copy or download the sanitized HTML.
Example
Edge cases
Unsafe HTML
Scripts, embedded active content, event attributes, and dangerous URL schemes are removed.
Remote content in preview
The preview uses a restrictive content policy and does not load remote images, styles, scripts, or fonts referenced by the Markdown.
Sanitization changes output
Unsupported tags and attributes are removed, and safe links receive nofollow, noopener, and noreferrer protection.
How it works
- Parses Markdown with optional GitHub-flavored extensions and hard line breaks.
- Runs generated markup through an allowlist sanitizer that removes active elements, event handlers, styling attributes, and unsafe URL schemes.
- Displays the result inside a scriptless sandbox with a network-blocking content policy while also exposing the HTML source.
Related workflows
Code Snapshot
Render pasted code as a styled SVG snapshot with syntax highlighting, themes, window frames, and gradient backgrounds for blogs and docs.
Case Converter
Convert text, identifiers, and variables between camelCase, snake_case, kebab-case, PascalCase, CONSTANT_CASE, Title Case, dot.case, and path/case.
Frequently asked questions
Does it execute embedded scripts?
No. Active elements and event handlers are stripped, and the visual preview is rendered in a scriptless sandbox.
Will remote Markdown images load in the preview?
No. Remote image requests are blocked in the local preview to preserve the no-fetch privacy boundary. The sanitized HTML may retain an HTTPS image URL for use after you deliberately publish it elsewhere.
Can I include raw HTML in Markdown?
Basic allowlisted elements can survive, but scripts, embeds, forms, metadata, inline event handlers, and unsupported attributes are removed.
References
- CommonMark Specification — Markdown parsing rules