Mermaid Live Editor & Viewer – Real-time interactive diagramming for developers

Summary: Mermaid Live Editor & Viewer is an open-source tool for creating, viewing, and editing Mermaid diagrams in real-time. It supports multiple diagram types and offers instant visualization without configuration. The tool evolved from a simple client-side viewer to a full-stack app with cloud sync and user accounts.

What it does

It provides an interactive online editor to write Mermaid code and instantly see rendered diagrams, including flowcharts, sequence diagrams, Gantt charts, and more. The application uses Next.js for the frontend and NestJS for the backend to enable persistence and cross-device access.

Who it's for

Developers and technical writers who need a distraction-free environment to create and preview diagrams-as-code efficiently.

Why it matters

It eliminates the need to switch contexts for diagram previews by offering a fast, dedicated workspace with cloud synchronization and user accounts.