UML Diagram Tool

A lightweight UML diagram tool for developers, architects, and students to create, edit, and share class, sequence, and activity diagrams online.

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About This Tool

This tool is a web-based UML diagram tool for software engineers, architects, educators, and product teams. It enables modeling of software structures and behavior by composing class, sequence, and activity diagrams, providing a precise and shareable representation of designs.\n\nConceptually, users select a diagram type, create elements such as classes with attributes and methods, actors or lifelines, and activities or states, and define relationships such as associations, generalizations, dependencies, or message flows. The tool validates semantic correctness and applies a layout engine to arrange elements for readability and consistency across diagrams.\n\nCore value lies in speed, clarity, and collaboration: teams can iterate designs quickly, keep diagrams in a shared workspace, and export to standard formats for reviews and documentation. It supports developers, architects, QA engineers, and educators who need precise, machine-readable artifacts that remain synchronized as requirements evolve.\n\nKey features include support for multiple diagram types, semantic validation, automatic layout, import/export of SVG PNG PDF, and a structured JSON representation for programmatic reuse. Typical use cases include modeling domain classes for APIs, detailing interaction flows in sequence diagrams, planning deployment views, and teaching UML concepts with real examples.

How to Use

  1. Choose diagram type and define scope.
  2. Add elements (classes, actors, lifelines, activities) and specify attributes, methods, or states.
  3. Create relationships and message flows between elements.
  4. Apply automatic layout and run validation to ensure consistency.
  5. Export or share the diagram in SVG, PNG, or PDF, or export the underlying diagram JSON for integration.
How to use free online tool for uml diagrams

Frequently Asked Questions

Find Quick Answers

Which diagram types are supported?
The tool supports class, sequence, and activity diagrams primarily, with support for use-case and state diagrams in limited form. Each diagram type provides dedicated element sets and relationship types, and the editor validates references to ensure coherence.
Can I export and share diagrams?
Yes. Diagrams can be exported as SVG, PNG, or PDF and can be shared via a link or embedded. Revision history is kept to track changes, and the exports preserve layout, connections, and element relationships.
Is it free and collaborative?
The core tool is free to use online; optional paid plans may unlock advanced features. Real-time collaboration allows multiple users to edit a diagram concurrently with versioning and change tracking.

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