mermaid

Validate Mermaid diagram syntax and rendering with the official Mermaid CLI.

17|Updated Feb 19, 2026

Search Tags:#documentation #mermaid #diagram validation #syntax checking #cli rendering #svg output

Ready to run

npx skills add https://github.com/ivanrvpereira/.agents --skill mermaid-ivanrvpereira

💬 Prompt for ChatGPT / Claude Chat▼

Please help me install this Agent Skill.
Skill: mermaid
Source: https://github.com/ivanrvpereira/.agents/tree/main/skills/mermaid
Command: npx skills add https://github.com/ivanrvpereira/.agents --skill mermaid-ivanrvpereira

SYSTEM DOCUMENTATION & REQUIREMENTS

💡 This Skill includes scripts (resource) components.

What problem does it solve?

Mermaid diagrams often fail at the last moment due to syntax errors or unsupported constructs, which wastes time during documentation and review cycles.

Core Features & Use Cases

Parse and render with the official Mermaid CLI to confirm Mermaid syntax is valid.
Generate a best-effort ASCII preview to quickly spot obvious layout issues without opening a browser.
Workflow for Markdown-safe diagrams by validating a standalone .mmd file before pasting into Markdown.

Use case: Validate a diagram.mmd before including it in a README or PR description so reviewers don’t hit broken diagrams in their rendered view.

Quick Start

Run the command to validate your file: ./tools/validate.sh diagram.mmd output.svg

Frequently Asked Questions about mermaid

High-intent search queries and answers about installing and using this skill.

FAQPage Schema

How do I validate Mermaid diagram syntax before adding it to Markdown?▼

You can validate Mermaid diagram syntax by running the official Mermaid CLI against a standalone .mmd file. The tool parses and renders the diagram, failing on non-zero exit codes to enforce correctness before you paste it into Markdown.

Can I generate an SVG output file when checking Mermaid syntax?▼

Yes, you can generate an optional SVG output file when validating Mermaid syntax. By providing an output path like output.svg to the validation script, the Mermaid CLI renders the diagram to SVG.

Do I need Node.js to run Mermaid syntax checking locally?▼

Yes, you need a Node-based execution environment because the validation runs via npx mermaid-cli. This dependency executes the official CLI to parse and render your .mmd files.

Why does my Mermaid diagram fail to render in a README?▼

Mermaid diagrams often fail to render due to syntax errors or unsupported constructs. Validating the .mmd file with the official Mermaid CLI before committing catches these errors during review cycles.

What is the best way to spot Mermaid layout issues without a browser?▼

The best way to spot obvious layout issues without a browser is to generate a best-effort ASCII preview. This feature runs alongside the Mermaid CLI validation to quickly confirm diagram structure.

Does this Mermaid CLI validation work with existing product documentation workflows?▼

Yes, this validation fits documentation and product workflows where diagrams are authored as .mmd files. It confirms syntax correctness before diagrams are pasted into PR descriptions or README files.