AI Mermaid diagram generator
Describe a process or a system in words and get Mermaid code for a flowchart, sequence, class, ER or Gantt diagram.
Your key stays in your browser.It goes straight to the provider, never to our servers, and we neither log nor keep it. Use a dedicated key with a spending cap, and delete it in the provider's dashboard when you are done.
Input
Result
The result will appear here.Mermaid turns a few lines of text into a diagram that GitHub, GitLab, Notion, Obsidian and most documentation tools render natively, which is why architecture notes increasingly live as Mermaid rather than as exported images nobody can edit. Writing the syntax by hand is the slow part. Describe the sign-up flow, the payment call chain or the data model in plain language, choose the diagram type, and the model returns Mermaid code only — no fences, no commentary — ready to paste into a Markdown file. To see it rendered, or to fix a label by hand, paste it into this site's Mermaid editor.
How it works
- The prompt is Fabric's create_mermaid_visualization pattern, adapted: its insistence that the diagram stand on its own is kept, its prose explanation section is dropped so the output is pure code, and a set of Mermaid syntax rules is added.
- Those rules target the mistakes that most often stop a generated diagram from rendering — unquoted labels containing brackets or non-ASCII text, a node called end, unclosed alt and loop blocks, colons inside Gantt task names.
- Labels and messages come back in the language you wrote in while IDs and keywords stay ASCII as the parser requires, and anything the model had to assume appears as a %% comment rather than as a silent invention.
- Your description reaches the AI provider directly from the browser, signed with your own key; diagram requests are small, so a throwaway key with a tight cap is plenty.
Where your data goes
With your own key, what you type and the key go from your browser straight to the provider you choose; neither passes through Hysen Labs. In hosted mode, your text goes through our server to our provider (DeepSeek) and is billed in credits; we keep the token counts and cost of each run for billing, never the text itself or the answer. How the provider handles the text is governed by its own privacy policy.
This tool handles keys and credentials, so nothing about a run is saved, not even to your own history.
About your API key
We do not collect, store or leak your key: it lives only in this page's memory (unless you tick “remember in this tab”) and is gone when you close it. Still, treat any key you have pasted into a web page with care — create a dedicated key with a spending cap for use here, and delete or rotate it in your provider's dashboard when you are done.
What it costs
This tool is free, with no sign-in and no points.
Common questions
- The code will not render. What should I check first?
- Paste it into the Mermaid editor and read the parser's error line. The usual culprits are a label with parentheses or quotes that was not wrapped in double quotes, a missing end after an alt or loop block, or ```mermaid fences the model added anyway — delete those. Regenerating with a larger model also fixes most syntax slips.
- Which diagram type should I pick?
- Flowchart for a process with decisions; sequence for requests passing between services or people over time; class for an object model; ER for database tables and their cardinalities; Gantt for a plan with durations and dependencies. When unsure, the flowchart is the most forgiving.
- Can it read my code and draw it?
- Paste the code as the description and ask for a class or sequence diagram, and it usually produces a reasonable sketch. It sees only what you paste, so a call chain spread over several files will come out incomplete; trim the input to the part you want drawn.
- Why are there no colours or styles?
- Styling syntax is where generated Mermaid breaks most often, and themes differ between GitHub, docs sites and editors. The code leaves styling to the renderer; add classDef lines yourself once the structure is right.
The open-source behind it
This tool's prompt is adapted from danielmiessler/Fabric (MIT) and runs on the model you choose. To use the same capability from the command line or inside your own program, start with that project.
danielmiessler/FabricAlso known as
- mermaid diagram generator
- text to flowchart
- ai flowchart generator
- mermaid ai
- sequence diagram generator
- er diagram from text