@mermaid-lint/cli

Validate Mermaid diagrams embedded in Markdown files. Uses the official mermaid.parse() API — catches real syntax errors, not just missing diagram-type keywords.

Full docs and examples →

Install

npm install --save-dev @mermaid-lint/cli
# or use without installing:
npx mermaid-lint

Usage

mermaid-lint                        # validate git-tracked *.md / *.mdx / *.markdown / *.mmd
mermaid-lint --all                  # scan every supported file on disk
mermaid-lint "docs/**/*.md"         # glob pattern (quoted to prevent shell expansion)
mermaid-lint --quiet                # failures only
mermaid-lint --format json          # machine-readable JSON output
mermaid-lint --strict               # treat semantic warnings as errors (exit 1)
mermaid-lint --no-semantic          # skip semantic checks (syntax errors only)

Exit codes: 0 = all valid · 1 = validation failures (or warnings with --strict) · 2 = usage/IO error

Configuration

Drop a mermaid-lint.config.js in your project root:

export default {
  files: ['docs/**/*.md', '**/*.mmd'],
  ignore: ['dist/**'],
  strict: false,
  semantic: true,
  format: 'text',
};

Pre-commit hook

npm install --save-dev husky lint-staged
npx husky init

package.json:

{
  "lint-staged": {
    "*.{md,mmd,mdx}": "mermaid-lint"
  }
}

.husky/pre-commit:

npx lint-staged