Mermaid Viewer

Mermaid Viewer is an online editor that renders Mermaid code live in the browser, adds GPT-4 code generation and error hints, and exports SVG, PNG or PDF. It offers sharing, templates and a free tier with paid yearly plans.

Mermaid Viewer is a browser-based editor and viewer for diagrams written in Mermaid syntax. Users paste or type Mermaid code, or open .mmd and .md content, and the rendered diagram appears alongside the code while they type, with no separate render step. The homepage lists a wide range of supported diagram types, including flowcharts, sequence, class, state and ER diagrams, user journeys, Gantt and pie charts, requirement diagrams, Git graphs, C4 diagrams, mind maps and timelines. The tool is aimed at developers, DevOps engineers, architects and technical writers who document systems in text but do not want to maintain a local Mermaid toolchain. It also reaches students and educators, as the template gallery includes academic examples such as a semester timeline and a course lifecycle. Using it in practice is a three-step loop: enter code, check the preview, then export to SVG, PNG or PDF. Exports can be tuned with custom DPI and dark or light themes, and Markdown output is also offered. Beyond rendering, the product adds several assistive features. An AI button turns a plain-text description into Mermaid code using GPT-4, syntax errors are highlighted with correction suggestions, and editor links can be shared so teammates can co-edit or comment. A template library provides ready-made starting points such as a governance committee decision flow and a wireframe collaboration flow. Larger organizations are pointed to a Docker private deployment with role-based access control, and a VS Code plugin is mentioned in a customer quote. The site states that no signup is needed to start and that data stays in the browser. Among alternatives, it sits between the bare official Mermaid live editor and heavier drag-and-drop diagramming suites. It keeps the text-first workflow of Mermaid while layering on sharing, version history and AI help. The free tier is deliberately limited (three diagrams, watermarked low-resolution PNG), so regular users are steered toward the paid Starter or Pro plans, which raise limits and unlock all export formats.