UMLet

UMLet is a free, open-source UML sketching tool for people who want to draft and export diagrams without adopting a full modeling workflow. Its direct, text-based editing suits quick changes; the lack of code generation and reverse engineering rules it out for teams needing diagrams linked to implementation.

Overview

UMLet covers class, use case, sequence, state, deployment, and activity diagrams. Rather than configuring elements through pop-up dialogs, users edit their text in a small markup dialect. That keeps changes direct, but favors lightweight sketching over a guided modeling process. The project dates to 2001 and is licensed under GNU GPL 3.0.

The stand-alone application exports diagrams to BMP, EPS, GIF, JPG, PDF, PNG, and SVG, and can copy them to the clipboard. It also supports command-line batch conversion of UXF files to formats such as PDF, which is useful when exports need to be repeated. UMLet does not generate code from models or models from code, and round-trip engineering is not planned. That is a decisive limitation for software teams expecting diagrams to stay aligned with implementation.

Key features

Editing element text instead of navigating dialogs can speed up drafting for users comfortable with UMLet's markup dialect. Custom UML elements can be written in Java and compiled on the fly, but only in the stand-alone version. This offers flexibility for Java-capable users, not a visual customization route for everyone.

UMLet is available as a stand-alone application, an Eclipse plugin, a browser app called UMLetino, and a Visual Studio Code extension. UMLetino runs without installation, saves diagrams in browser storage, and exports PNG. The stand-alone app has broader export options and batch conversion. The change history records an XML security fix in version 14.3.

Pricing

Both plans are free at no cost. The UMLet plan includes the stand-alone apps for Windows, macOS, and Linux, plus the Eclipse plugin, web app, and VS Code extension. UMLetino is the browser-based option, with browser storage and PNG export. Choosing UMLetino means giving up the stand-alone app's broader export formats, clipboard copying, batch conversion, and Java-based custom elements.

Platforms

The stand-alone application runs on Java platforms including Windows, Linux, and macOS, and requires Java to be installed. The browser app needs no installation and stores diagrams in browser storage. Users can also access UMLet through Eclipse and Visual Studio Code extensions. Bug reports and feedback go to [email protected] or a GitHub ticket.

Who it's for

UMLet fits students and practitioners who need to sketch common UML diagrams quickly, make direct text edits, and export or batch-convert files without paying for a modeling tool. It is less suitable for teams that need code generation, reverse engineering, or a round-trip connection between diagrams and source code.

Pros and cons

• Pros: Free and open source across desktop, browser, Eclipse, and VS Code options, so users can choose a convenient entry point.
• Pros: The stand-alone app supports seven export formats, clipboard copying, and command-line batch conversion, useful for varied delivery and repeatable output.
• Pros: Java-based custom elements allow stand-alone users to extend the available diagram components.
• Cons: Editing depends on a small markup dialect, which may be less approachable than dialog-based configuration for users who prefer a visual workflow.
• Cons: UMLet has no code generation, reverse generation, or planned round-trip engineering, making it a poor fit for model-driven development.
• Cons: The stand-alone application requires Java, while UMLetino offers only PNG export.

Alternatives

For a UML modeling environment with multi-user projects, consider Sparx Enterprise Architect; it has a free plan and trial, with custom pricing for its Professional — Standard License plan.

BESSER is another free, open-source option, with API, self-hosted, web, and desktop platforms. ArgoUML is a free, open-source option for Linux, macOS, and Windows, licensed under EPL 1.0 and requiring Java 5 or later. BOUML is free to use on Linux, macOS, and Windows. BridgePoint offers a free, Apache 2.0-licensed open-source plan with an editor, verifier, and model compilers. Eclipse Papyrus is a free open-source modeling environment with no usage limits stated. Gaphor is a free, Apache 2-licensed open-source option for Linux, macOS, and Windows.

Browse our UML Modeling Software and Diagramming Software lists for more options.

Verdict

Choose UMLet if you want a free, lightweight way to sketch UML and export diagrams across desktop and browser workflows. Its direct editing and useful stand-alone export tools are the main draw; look elsewhere if diagrams need to generate code or remain synchronized with it.