Online Markdown editor and preview
Write or paste Markdown in your browser and see it rendered live, with GitHub-flavoured tables and task lists, LaTeX maths, syntax-highlighted code and Mermaid diagrams — all rendered on your own machine.
Open the Markdown viewerNo signup. Nothing uploaded.
Why a viewer rather than a text editor
Most Markdown previews stop at headings and bold text. The ones that matter — a table that has to line up, a formula, an architecture diagram — are exactly the ones a basic preview gets wrong, so you end up pushing a commit to find out how it looks.
Ways to read a Markdown file
- Preview
- GitHub-flavoured Markdown: tables, task lists, strikethrough and autolinks. LaTeX maths through KaTeX, code blocks highlighted by language, a generated table of contents, and heading anchors so any section can be linked.
- Mermaid diagrams
- A ```mermaid fence is drawn as a diagram rather than shown as source — flowcharts, sequence diagrams, class diagrams, state machines, Gantt charts and more. Diagrams follow the app’s theme, download as SVG, and a syntax error is reported inline without breaking the rest of the document.
- Code
- Monaco with Markdown highlighting and folding, so a long document stays navigable while you edit it.
What people use it for
- Checking a README before you push
- The preview renders what GitHub renders, including the table you are not sure about and the badge row at the top.
- Drafting documentation
- The table of contents updates as you write, and every heading gets a stable anchor you can link to.
- Drawing an architecture diagram
- Write it as Mermaid, see it drawn, download the SVG. No diagramming tool, no account, no image to keep in sync with the text.
- Converting a table
- A Markdown table converts to CSV or JSON when you need the data rather than the document.
What it checks in your Markdown
- Unterminated code fences
- Front matter that is not valid YAML
- Raw HTML is sanitised through an allow-list before rendering, so a document containing a script tag renders inert
Privacy
The file is read by your browser and parsed on your own machine. No request carries its contents — you can confirm that in your browser's network panel, or by disconnecting from the network and using the app anyway. There is no account, and nothing is stored on a server because there is no server.
File types it opens
.md, .markdown, .mdown, .mkd — and any file you paste, whatever its name. Up to 50 MB by default, adjustable to 500 MB in Settings.
Questions
Is there a free online Markdown editor with live preview?
Yes. fileviewer.dev renders Markdown as you type, with GitHub-flavoured tables and task lists, LaTeX maths, highlighted code and Mermaid diagrams. It is free, needs no account, and renders everything in your browser.
Does it support Mermaid diagrams?
Yes. A fenced block marked mermaid is rendered as a diagram — flowcharts, sequence and class diagrams, state machines, Gantt charts, and the rest of Mermaid’s types. Diagrams follow the current theme and download as SVG. A diagram with a syntax error reports it inline and leaves the rest of the document rendered.
Does it support LaTeX maths?
Yes, through KaTeX. Inline maths uses single dollar signs and display maths uses double, the same as on GitHub.
Is raw HTML in my Markdown safe to render?
It is sanitised before it reaches the page. Raw HTML is parsed into nodes and then filtered through an allow-list, so tags and attributes that are not explicitly permitted — script elements, event handlers, javascript: URLs — cannot render. Details and summary elements, and the tags KaTeX needs, are permitted because documents genuinely use them.
Is my document uploaded anywhere?
No. Rendering happens entirely in your browser, including the Mermaid diagrams. Nothing is sent anywhere, and the editor works offline.