Mermaid Diagram Editor
Write flowcharts, sequence diagrams, and more as text — rendered live
Diagram preview will appear here…
About this tool
The Mermaid Diagram Editor renders flowcharts, sequence diagrams, class diagrams, state diagrams, Gantt charts, pie charts, and entity-relationship diagrams from plain text — using the same Mermaid syntax that renders natively in GitHub, GitLab, and Notion markdown. Writing a diagram as text instead of dragging boxes in a GUI means it can live in version control, get reviewed in a pull request like any other code change, and stay in sync with the codebase it documents — rather than going stale in a separate design tool nobody remembers to update.
When to use it
- →Drafting a sequence diagram for an API flow or a system design doc before writing the implementation
- →Writing architecture diagrams that live in the repository as text and get reviewed in pull requests
- →Creating a flowchart to document a decision process or onboarding workflow
- →Exporting a diagram as SVG or PNG to drop into a slide deck or external documentation
Tips
- ◆Diagrams written in Mermaid syntax render natively in GitHub and GitLab markdown — write it once here, verify it looks right, then paste it straight into a README's code fence.
- ◆Start from one of the built-in templates (Flowchart, Sequence, Class, State, Gantt, Pie, ER) and modify it — it's faster than writing Mermaid syntax from a blank page.
- ◆SVG export stays crisp at any zoom level for documentation; PNG export is better for pasting directly into tools that don't render SVG well, like some slide software.
- ◆Keep node labels short — Mermaid's automatic layout engine handles long labels by making the diagram wider, which can push it off the page in exports.
Frequently asked questions
Where else can I use the diagrams I write here?
Anywhere Mermaid is supported natively — GitHub and GitLab render ```mermaid code fences directly in markdown (READMEs, issues, pull requests), as does Notion. Paste the exact same syntax you wrote here into any of those and it renders identically, no image export required.
Why did my diagram fail to render?
Mermaid syntax is diagram-type-specific — a flowchart uses graph TD or graph LR as its first line, a sequence diagram uses sequenceDiagram, and so on. The most common cause of a render failure is mixing syntax from two different diagram types, or a typo in an arrow (-->) or connector. Start from the matching template and modify incrementally to isolate what broke.
Is Mermaid the same as diagrams made in Lucidchart or draw.io?
Different approach entirely. Lucidchart and draw.io are GUI-based, drag-and-drop diagramming tools that produce a proprietary file format. Mermaid diagrams are plain text — which means they diff cleanly in version control, can be generated programmatically, and don't require a specific paid tool to open and edit. The tradeoff is layout control: Mermaid's automatic layout engine positions elements for you, rather than pixel-perfect manual placement.
Can I control the exact position of each node?
Not precisely — Mermaid uses an automatic layout algorithm rather than manual positioning, which is the core tradeoff for writing diagrams as text instead of dragging shapes. You can influence layout indirectly through diagram direction (TD, LR, etc.) and the order nodes are declared, but pixel-level control isn't part of the Mermaid model.