PlantUML open-source diagram tool: text-to-UML syntax, sequence and class diagrams, free GPL license, features and alternatives like Mermaid compared.
PlantUML was first released in 2009 by developer Arnaud Roques as a way to generate UML diagrams directly from plain-text descriptions rather than manual drag-and-drop editors. It has since become one of the most widely adopted diagrams-as-code tools in software development.
As an open-source project distributed under the GPL license, PlantUML has no company, funding, or commercial pricing behind it. It is maintained by its original author alongside a community of contributors on GitHub, and is free to download, self-host, or use through public and private PlantUML servers.
PlantUML supports the full range of classic UML diagram types, including sequence, class, use case, activity, component, state and deployment diagrams, all defined with a concise, human-readable text syntax.
Beyond UML, it supports ArchiMate, BPMN-style diagrams, C4 model diagrams, Gantt charts, mind maps, wireframes, entity-relationship diagrams and network diagrams, plus direct visualization of JSON and YAML data, making it useful well beyond strict UML modeling.
PlantUML is entirely free and open source under the GPL license. There are no paid tiers, subscriptions, or feature gates for the core tool itself.
Costs, if any, come from optional infrastructure choices, such as running a self-hosted PlantUML server at scale or paying for third-party plugins, hosting, or documentation platforms that embed PlantUML rendering, rather than from PlantUML itself.
Yes, PlantUML is completely free and open source, distributed under the GPL license.
PlantUML was created by developer Arnaud Roques and first released in 2009.
It supports UML diagrams like sequence, class, use case, activity and state diagrams, plus ArchiMate, BPMN-style flows, C4 diagrams, Gantt charts, mind maps and more.
Yes, PlantUML can be run locally, as a self-hosted PlantUML Server, or accessed through public rendering servers.
Both are text-to-diagram tools, but Mermaid renders natively inside GitHub and many Markdown viewers by default, while PlantUML supports a broader range of diagram types and typically requires a rendering server or plugin.
Some PlantUML diagram types rely on the Graphviz layout engine for rendering, so self-hosted setups often need Graphviz installed.
Yes, PlantUML integrates with tools like Confluence, VS Code, IntelliJ and many documentation and static site generators.