AI models are surprisingly good at writing Mermaid. Describe what you want in plain English and MermaidViewer's AI diagram generator produces valid Mermaid code that renders instantly — then you can refine it by hand or with more instructions.
The anatomy of a good prompt
- Diagram type — "a sequence diagram", "an ER diagram". If you don't specify, the AI picks the most suitable type.
- Actors or entities — who or what appears in the diagram.
- Steps and branches — the happy path plus important alternatives and errors.
- Constraints — direction (left to right), level of detail, labels to include.
Prompt examples
| Goal | Prompt |
|---|---|
| Flowchart | Flowchart, left to right, of our refund process: request, eligibility check, manager approval for amounts over $500, refund, email confirmation. |
| Sequence | Sequence diagram of a mobile app logging in with Google via our backend, including token refresh. |
| ER | ER diagram for a gym: members, memberships, classes, trainers, bookings, with keys. |
| Gantt | Gantt chart for a 6-week website redesign starting March 2, 2026, excluding weekends. |
Four AI actions in the editor
- Generate — create a new diagram from a description.
- Edit — change the current diagram with an instruction such as "add a caching layer" or "translate labels to Spanish".
- Fix — repair syntax errors using the parser's error message.
- Explain — get a plain-English explanation of a diagram, useful for reviews and accessibility.
Convert existing content
You can paste source material — SQL CREATE TABLE statements, a list of API endpoints, meeting notes or a bullet outline — and ask for the matching diagram type. This is the fastest way to document an existing system.
Free accounts get a daily AI quota; Pro raises it substantially. Anonymous visitors can try AI a few times per day without signing up.