What it is
Mermaid is a project for diagrams as code. Instead of opening a separate drawing tool, a developer writes a small text block and Mermaid renders a flowchart, sequence diagram, Gantt chart, mind map, C4 diagram, state diagram, or another technical visual.
The point is not to replace Figma or heavyweight architecture tools. Mermaid fits a narrower job: explain a process, data flow, call order, or system structure directly inside Markdown documentation, pull requests, wikis, or internal guides.
How it appeared and what is inside
Mermaid grew out of a documentation problem: diagrams become stale faster than text, especially when they are stored as exported images. A text diagram can be edited with the surrounding document, reviewed in Git history, and updated without manually exporting a new image.
The repository contains the TypeScript library, diagram syntaxes, parsers, rendering logic, documentation, tests, and integration work around the Mermaid ecosystem. One practical advantage is GitHub Markdown support, which makes many simple diagrams visible directly in repositories.
Markdown diagram example
This snippet shows the normal use case: the diagram lives as text, so it can be changed in the same pull request as the documentation.
```mermaid
flowchart TD
idea[Idea] --> draft[Draft]
draft --> review[Review]
review --> publish[Publish]
```Where it helps
Mermaid is useful for API documentation, business processes, deployment diagrams, onboarding notes, architecture explanations, and any material where a quick visual relationship matters. It is especially convenient for teams that already use Markdown heavily.
Strengths and limits
The main strength is the low entry barrier. A useful diagram can be only a few lines long. Another strength is reviewability: text diagrams are easy to discuss, copy, version, and translate, which makes them natural for documentation that evolves with code.
The tradeoff is visual control. Mermaid works best for clear technical diagrams, not for polished branded infographics. If pixel-perfect layout or complex visual composition matters, a dedicated design tool is still a better fit.