UMLet

UMLet is a free, open-source tool for making UML sketches, with desktop, browser, Eclipse and Visual Studio Code options. It is best for people who want to draft and export diagrams without taking on a full modeling workflow.

Its text-based editing makes quick changes direct, but the same sketch-first focus rules it out for teams that need models connected to code.

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. This keeps changes close to the diagram, but asks users to learn UMLet’s editing conventions.

The stand-alone application exports diagrams to BMP, EPS, GIF, JPG, PDF, PNG and SVG, and can copy them to the clipboard. Command-line batch conversion of UXF files is useful when diagrams need repeated exports. UMLet does not generate code from models or reverse-generate models from code, and round-trip engineering is not planned; it is therefore a poor fit for teams that expect diagrams to track implementation.

Key features

Users can create custom UML elements by writing Java code, which UMLet compiles on the fly. That gives Java-capable users a route to tailored elements, but it is available only in the stand-alone application.

UMLet comes as a stand-alone app, an Eclipse plugin, a browser app called UMLetino and a Visual Studio Code extension. UMLetino runs without installation and saves diagrams in browser storage, which is convenient for browser-based work but ties saved diagrams to that storage. The project identifies UMLet as open source under GNU GPL 3.0. Its change history records an XML security fix in version 14.3.

Pricing

Both plans are free at free. The UMLet plan includes the stand-alone app for Windows, macOS and Linux, plus the Eclipse plugin, web app and VS Code extension. It is the broader option for users who want desktop exports, batch conversion or custom Java elements.

UMLetino is also free at free. It runs in a browser, saves diagrams in browser storage and exports to PNG. Choose it for lightweight browser work; choose the UMLet plan when you need the stand-alone app’s broader export formats or other desktop-only capabilities. No paid tier is part of either plan.

Platforms

The stand-alone app runs on Java platforms including Windows, Linux and macOS, and requires Java to be installed. UMLet also runs in a browser and is available as Eclipse and Visual Studio Code extensions. Bug reports and feedback can be sent by email or submitted as a GitHub ticket.

Who it's for

UMLet suits students, developers and other practitioners who need quick UML sketches, direct text edits and practical export options at no cost. Its desktop and browser variants let users choose between a fuller export workflow and a no-install option. It is not suited to teams seeking code generation, reverse engineering or round-trip model maintenance.

Pros and cons

Pros

Free, open-source access across desktop, browser, Eclipse and Visual Studio Code makes it easy to choose a working context without a paid plan.

The stand-alone app’s range of export formats, clipboard copy and UXF batch conversion support both one-off diagrams and repeated output jobs.

Text-based editing favors direct adjustments, while Java custom elements offer extra flexibility in the stand-alone version.

Cons

The markup-based workflow is less suited to users who want to configure diagrams through guided dialogs.

Custom elements require Java and are confined to the stand-alone app.

No code generation, reverse generation or planned round-trip engineering means diagrams will not serve as a code-linked modeling workflow.

UMLetino saves in browser storage and exports PNG, so it lacks the stand-alone app’s broader export choices.

Alternatives

Sparx Enterprise Architect is worth considering when UMLet’s sketch-first scope is too narrow: it is freemium, has a free plan and trial, and its Professional Standard License is described as a UML modeling environment with multi-user projects.

BESSER is another free, open-source option, with web, desktop, self-hosted and API platforms. Horusec is a free Apache-licensed alternative with CLI and platform components. kUML is free and open source under Apache 2.0. Modelio offers a free open-source modeling environment, though downloadable extensions may require separate licenses. ArgoUML is a free, open-source Java 5+ option under EPL 1.0. BOUML and BridgePoint are also free choices; BridgePoint’s open-source plan includes an editor, verifier and model compilers.

Browse more options in UML Modeling Software or Diagramming Software.

Verdict

Choose UMLet if you want free, fast UML sketches with desktop exports and several ways to access the editor. Its direct text workflow and batch conversion are practical strengths; the decisive limitation is that it stops at diagrams, with no code generation or model-code loop. For code-connected modeling, look elsewhere.