Free Mermaid viewer · No sign-up · Nothing uploaded

Mermaid Viewer — view Mermaid diagrams online

Paste Mermaid code from ChatGPT, Claude or a README and see the diagram instantly. Zoom, fix, export — all in your browser.

View any Mermaid diagram in seconds

Mermaid turns a few lines of text into flowcharts, sequence diagrams, ER diagrams, Gantt charts and more. The catch is that you need something to render it. GitHub and Notion only show diagrams inside their own pages, and AI chat apps hand you the raw code. This Mermaid viewer fills the gap: paste the code, and the diagram appears on the right a moment after you stop typing.

How to use the viewer

  1. Paste Mermaid code into the editor, or upload a .mmd, .mermaid, .md or .txt file. You can also drag a file onto the tool.
  2. If the paste still has its ```mermaid fence, the fence is removed for you. If you paste a whole Markdown document, every diagram in it is found and you pick which one to view.
  3. Drag to pan, use + / − or Ctrl/⌘ + scroll to zoom, and Fit (or a double-click) to frame the whole diagram.
  4. Choose a theme — default, neutral, dark or forest — and turn on a transparent background if the image is going onto a coloured slide.
  5. Download a PNG (1x, 2x or 3x) or an SVG, copy the SVG code or the PNG itself, or copy a share link.

When a diagram does not render

AI-generated Mermaid often breaks on small things: parentheses inside a label, a node called end, a -> arrow or Chinese punctuation. Instead of the parser's raw message, the viewer tells you what went wrong in plain English, highlights the line, and offers Try to fix. The fixer shows exactly what it would change and waits for you to apply it. For a deeper look, the Mermaid syntax fixer keeps the repair panel open the whole time.

Private by design

Rendering, fixing and exporting all happen in your browser. Your code is never sent to a server — even share links keep the diagram inside the URL fragment, which browsers do not send to us. Your last diagram is saved in this browser's local storage, so a refresh does not lose your work.

Related tools

Need a file for a slide deck? Use Mermaid to SVG for editable vectors or Mermaid to PNG for images that paste anywhere. Have a long Markdown document with several diagrams? Extract them all at once, or open the file in the MD viewer, where every diagram has its own export buttons.

FAQ

Is this the official Mermaid Live Editor?

No. openmdfile is an independent tool built on the open-source Mermaid library (version 10.9.1). It focuses on viewing, fixing and exporting diagrams; it is not affiliated with the Mermaid project.

Is my Mermaid code uploaded anywhere?

No. The diagram is rendered by JavaScript in your browser. Nothing you paste or upload is sent to our servers, and share links store the code in the URL fragment, which is never sent to a server.

Which diagram types can I view?

Flowcharts, sequence, class, state, ER, Gantt, pie, user journey, mindmap, timeline, git graph, quadrant, requirement, C4, sankey, XY and block diagrams — everything Mermaid 10.9 supports.

Can I open .mmd or .mermaid files?

Yes. Click Upload file or drag the file onto the tool. Markdown files work too; if one contains several diagrams, you choose which to view.

Why does my diagram show an error?

Usually it is a small syntax problem such as brackets inside a label or a node named end. The viewer explains the error, highlights the line and can try a rule-based fix that you review before applying.