IconVault's Mermaid Editor lets you write Mermaid diagram code and see it rendered as SVG instantly. Start from samples for flowcharts, sequence diagrams, class diagrams, state diagrams, Gantt charts, pie charts, mindmaps and timelines, pick a theme, and watch the live preview update as you type, with clear error messages when the syntax is off.

Export your finished diagram as SVG or PNG for docs, READMEs and presentations. The Mermaid library loads on demand and everything runs fully in your browser with nothing uploaded. It is free to try (repeated use may ask for Pro).