Markdown Editor
Write Markdown with an instant, sanitized preview.
Markdown guide
# Heading**bold text**_italic text_[label](https://example.com)- List item1. List item> Quoted text`code````js ... ```---- [ ] To doUse the sample button to restore a complete example with headings, lists, code, quotes, links, and a table.
How to use the Markdown editor
- Add your Markdown. Type it in the left pane, or upload a local .md or .txt file.
- Watch the live preview. The rendered output on the right updates as you type.
- Export. Click "Copy HTML" or "Download .html" to save the rendered result.
What happens to your document
Rendering happens entirely in your browser tab, and the preview is sanitized with DOMPurify before it's displayed. An uploaded file is read into memory on your device — it's never sent to OpenToolkit.
Because everything runs locally, a very long document is bound only by your browser's memory and rendering performance, not a server-side limit.
What this editor supports
Common reasons to use this editor
- Draft a README or changelog with instant formatting feedback.
- Turn notes into clean HTML for a blog post or internal wiki page.
- Check how GitHub-flavored tables and code blocks will actually render.
- Sanity-check Markdown before pasting it into a CMS or issue tracker.
Frequently asked questions
Is my document uploaded anywhere?
No. Rendering and sanitizing the preview both happen in your browser tab; an uploaded file stays on your device.
Why is the preview sanitized?
DOMPurify strips scripts and unsafe HTML from the rendered preview, so the tool stays safe even if your Markdown contains raw HTML.
What Markdown syntax is supported?
GitHub-flavored Markdown — tables, fenced code blocks, lists and the other syntax GitHub renders.
Can I open a local file?
Yes — upload a local .md or .txt file to load it straight into the editor.
Is there a document size limit?
No fixed limit, but a very long document can slow the live preview since everything runs in one browser tab.
Can I export back to plain HTML?
Yes — use "Copy HTML" or "Download .html" to get the rendered output as standalone HTML.
Last reviewed: August 2026