Mermaid
Generate diagrams from text
The Lens
By Erik Loyd, SaaS CEO and former COO/CFO of an AWS Premier Partner.
Updated Aug 2026
Mermaid turns plain text into diagrams. Flowcharts, sequence diagrams, ERDs, Gantt charts, and git graphs, plus newer types like architecture diagrams, kanban boards, treemaps, radar charts, and Wardley maps. The library is MIT, and GitHub, GitLab, Obsidian, and Notion render it natively, so a fenced code block in a README becomes a picture with no image file to keep in sync.
Cost to run: zero. It is a JavaScript library you drop into a page, or nothing at all when your host already renders it. No service, no account, no build step beyond what you already have.
The commercial side moved to mermaid.ai and rebuilt itself around AI credits. Basic is free but caps you at six diagrams and 15 AI credits. Plus is $12 per user per month, or $120 a year, with unlimited diagrams and 300 AI credits. Premium is $24 per user per month, or $240 a year, adding SSO and unlimited viewer seats. None of it is required, at any team size. The syntax and the renderer stay MIT.
The catch: complex diagrams get messy fast. Past thirty or so nodes the auto layout starts making bad choices and you cannot hand-position anything to fix it. For polished presentation work, excalidraw/excalidraw or a real design tool still wins. Mermaid is for diagrams that live next to code.
Free vs Self-Hosted vs Paid
fully freeFree
The mermaid library, MIT licensed, current release 11.16.1 (2026-08-04). Every diagram type, the full renderer, no paywall, no telemetry gate. GitHub, GitLab, Obsidian, Notion, and many static site generators render it server side, so plenty of teams never install anything.
Paid (Mermaid Chart, now at mermaid.ai)
A separate hosted editor built on top of the library, restructured around AI credits:
- Basic: $0. Up to six diagrams, limited diagram size, 15 AI credits.
- Plus: $12/user/mo, or $120/user/yr which works out to $10/mo. Unlimited diagrams, unlimited size, 300 AI credits a year.
- Premium: $24/user/mo, or $240/user/yr which works out to $20/mo. 2,000 AI credits a year, unlimited free viewer seats, unlimited teams and projects, SSO.
- Enterprise: quoted. Custom contracts, invoicing, diagram ownership transfer to an admin, a dedicated CSM.
Self-Hosted Costs
$0. There is nothing to host. Add the npm package or a script tag, or write the code block and let your platform render it.
When to Pay
Pay only when non-technical teammates need a visual editor or AI generation, or when SSO is a requirement rather than a nice to have. For anyone writing the syntax by hand, the paid product adds convenience and nothing else. Nothing in Mermaid's syntax is gated behind a plan.
The library is MIT with zero paywalls. Mermaid Chart at mermaid.ai is an optional editor: free Basic, Plus $12/user/mo, Premium $24/user/mo. You never need it.
What to do by team size
- Solo
- free; the library does everything, skip the hosted editor
- Small team
- free; standardize on Mermaid for the diagrams that live in the repo
- Medium team
- free; Plus at $12/user/mo only if non-technical teammates want the visual editor and AI
- Large team
- free; Premium at $24/user/mo buys SSO and viewer seats, but the renderer itself costs nothing
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