UML (Unified Modeling Language) diagrams are essential for software design, system architecture, and team communication. Our online UML diagram editor supports both PlantUML and Mermaid.js -- the two most popular text-based diagramming languages -- so you can use whichever syntax you prefer.
Unlike drag-and-drop tools, text-based diagrams are version-controllable, easy to share, and quick to modify. Store your diagrams in Git alongside your code, review them in pull requests, and keep your documentation always up to date.
The live preview updates as you type, so you can see your changes instantly. Our editor includes syntax highlighting, auto-completion, and error diagnostics to help you write diagrams faster. Choose from built-in themes and templates for sequence diagrams, class diagrams, activity diagrams, state machines, ER diagrams, flowcharts, Gantt charts, and more.
Work with multiple diagrams using tabs, share via URL, and export as SVG or PNG for documentation, presentations, or code reviews. Whether you are a software engineer documenting an API flow, a system architect mapping microservices, or a student learning object-oriented design, this online UML tool has you covered.
PlantUML offers 15+ diagram types and 40+ visual themes, while Mermaid.js renders entirely in your browser and is natively supported in GitHub Markdown, GitLab wikis, Notion, and many other documentation platforms. No installation, no Java, no plugins -- just open the editor and start diagramming.
The UML Diagram Editor on FindUtils is a browser-based tool for creating professional UML diagrams using text-based syntax. It supports both PlantUML and Mermaid.js, giving you the flexibility to choose the engine that best fits your workflow. PlantUML excels at complex diagrams with 15+ types including sequence, class, component, deployment, and timing diagrams, while Mermaid.js renders entirely client-side and integrates natively with GitHub, GitLab, and Notion. The built-in AI assistant lets you describe diagram changes in natural language and applies the generated code directly to the editor.
Text-based diagramming solves a core problem in software documentation: keeping visuals in sync with code. Unlike drag-and-drop tools such as Lucidchart or draw.io, PlantUML and Mermaid source files are plain text that lives in your Git repository. This means diagrams are versioned, diffable, and reviewable alongside the code they describe. Our editor enhances this workflow with live preview, syntax highlighting, auto-completion, and one-click export to SVG or PNG. For database modeling, pair this tool with the ER Diagram Designer. For mapping service architectures, try the Architecture Diagram tool. If you need to visualize state transitions, the State Machine Designer provides a dedicated canvas.
Whether you are writing technical specifications, preparing a design review, or building course materials, the UML Diagram Editor handles everything from quick sketches to detailed system models. Combine it with the Markdown Previewer to embed Mermaid diagrams in your documentation, or use the Code Screenshot Generator to share polished diagram code snippets on social media. All processing happens in your browser -- no signup, no file uploads, and no usage limits.