Diagram Gpt

DiagramGPT is a small web app that draws diagrams from a plain language description. Users describe what they want, and the app asks an OpenAI model to write Mermaid code, then renders the result beside the conversation. It supports flowcharts, sequence diagrams, class diagrams, user journeys, Gantt charts and C4 diagrams. It suits developers, architects and technical writers who want a quick diagram without learning Mermaid syntax. The interface works as a chat, so a diagram can be refined over several messages, and the generated code can be copied, exported as SVG, or opened in the Mermaid Live Editor for manual changes. The app is built with Next.js, the shadcn user interface components and Mermaid.js, and the source code is public on GitHub for anyone who wants to run it locally. There is no pricing and no account. The app is free to use, but it requires the user's own OpenAI API key, which is stored in the browser, and any model usage is billed by OpenAI to that key. This is a personal project by the developer Fraser Xu rather than a commercial product. The most recent commits to its repository date from April 2025, so model options and features may lag behind newer diagramming tools.