What Mermaid errors does this validator show?

It uses Mermaid’s own browser parser and preserves its parse message, line number, source context, and caret marker when available.

Does the Mermaid validator render a preview?

Yes. Valid source renders as a live SVG preview while you edit, so you can check the diagram before exporting it.

This page does not create downloads. After validation, use its links to the dedicated Mermaid to PNG, SVG, or WebP tools.

No. Syntax validation and live preview are available without an account.

No. Pasted and uploaded Mermaid source is parsed and previewed locally in your browser on this validator page.

Validate Mermaid syntax with line-level errors and a live diagram preview.

Your diagram stays in this browser while it is validated.

Paste text

Checks locally as you edit

Paste Mermaid source or upload an .mmd file to check its syntax and preview the diagram.

Privacy and limitsProcessed in your browser. Files are not uploaded. Files up to 2 MB.

Files are processed in your browser and are not uploaded.

Files can be up to 2 MB.

Validate Mermaid syntax, choose another export format, or review the diagram guide.

1Paste Mermaid source into the editor or upload an .mmd or .mermaid file.
2Wait for the browser-local syntax check and live preview to update.
3If the source is invalid, use Mermaid’s line and caret details to find the error.
4Once the diagram is valid, continue to the PNG, SVG, or WebP export tool.

What Mermaid errors does this validator show?: It uses Mermaid’s own browser parser and preserves its parse message, line number, source context, and caret marker when available.
Does the Mermaid validator render a preview?: Yes. Valid source renders as a live SVG preview while you edit, so you can check the diagram before exporting it.
Can I export the validated diagram here?: This page does not create downloads. After validation, use its links to the dedicated Mermaid to PNG, SVG, or WebP tools.
Do I need to log in?: No. Syntax validation and live preview are available without an account.
Is my Mermaid source uploaded?: No. Pasted and uploaded Mermaid source is parsed and previewed locally in your browser on this validator page.