What this tool does
Runs a bounded, browser-local syntax preflight for common Mermaid diagram families and renders simple flowcharts to safe SVG or PNG.
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🧜 Mermaid Syntax Validator
Preflight common Mermaid syntax locally with bounded diagnostics, then render simple flowcharts to SVG or PNG.
Runs locally in your browser. Supports flowchart, sequence, class, state, ER, gantt, and pie preflight checks up to 100,000 bytes.
INPUT_TOO_LARGE, UNSUPPORTED_DIAGRAM_TYPE, UNSUPPORTED_RENDER_DIAGRAM, and PNG_OUTPUT_TOO_LARGE are typed failures. Rendering supports simple flowchart edges only and never claims full Mermaid parity. PNG download is browser-local PNG conversion of the same sanitized SVG; nothing is uploaded. See Artifact Ops boundaries or the HTTP and MCP contract. Need another format? Request a named output.
Why it is useful
It catches malformed delimiters, quotes, unsupported diagram headers, and invalid sequence statements before source reaches the renderer.
Honest rendering boundary
This is not full Mermaid renderer parity. Rendering supports simple flowchart edges only; other supported diagram families remain validation-only.
Privacy note
Runs locally in your browser. Diagram source, SVG, PNG, and diagnostics are never uploaded.
Important limitation
No automatic repair is performed. Correct the source yourself, validate again, then copy the reviewed source or download the browser-local PNG.