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JetUML

jetuml.org

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Spec score 7.6 #16 of 26 in UML Modeling Software

What it is

JetUML is a free desktop editor for sketching software designs with UML. It supports class, sequence, state, object, and use case diagrams, keeping its feature set focused on core diagramming. Association edges are laid out automatically, and moving nodes changes their paths. A validity check reports diagram problems through temporary notifications. You can export diagrams as SVG, PNG, or JPEG images, or copy them to the system clipboard for use elsewhere. JetUML saves diagrams as JSON in a documented open format with a schema for each diagram type. It runs on Windows, macOS, and Linux. Distribution uses Java archives, including an operating-system-independent archive that requires Java and JavaFX; a community Nix package is available for macOS and Linux. The application is licensed under GNU GPL version 3 or later. JetUML states that it collects no information and accesses the network only to open Help-menu web pages. Larger diagrams can reduce performance.

Spec sheet

Purpose
JetUML is a desktop UML editor for quickly sketching software design ideas.Read 7 Oct 2026 · jetuml.org
Privacy
JetUML states that it collects no information and accesses the network only to open web pages through Help menu commands.Read 7 Oct 2026 · jetuml.org
Support
The project invites users to send endorsements to [email protected] and to support it by starring its GitHub repository.Read 7 Oct 2026 · jetuml.org
License
The application is distributed under the GNU General Public License version 3 or later.Read 7 Oct 2026 · jetuml.org
Automatic layout
JetUML automatically lays out association edges, and moving nodes changes their paths.Read 7 Oct 2026 · jetuml.org
Diagram types
It supports class, sequence, state, object, and use case diagrams.Read 7 Oct 2026 · jetuml.org
Export and clipboard
Diagrams can be exported as images, including SVG, PNG, and JPEG, or copied to the system clipboard for use in other applications.Read 7 Oct 2026 · jetuml.org
File format
JetUML stores diagrams as JSON using a documented open format, with a schema for each diagram type.Read 7 Oct 2026 · jetuml.org
Intended use
The project describes its focus as a minimalist set of core UML diagramming features for fast sketching.Read 7 Oct 2026 · jetuml.org
Notable limitation
The user guide says larger diagrams decrease application performance.Read 7 Oct 2026 · jetuml.org
Platforms and installation
The application is distributed as Java archives, including an OS-independent archive requiring Java and JavaFX; a community Nix package is available for macOS and Linux.Read 7 Oct 2026 · jetuml.org
Validation
It checks diagram validity and reports problems with temporary notifications.Read 7 Oct 2026 · jetuml.org

Plans and prices

JetUML Free Free and open-source UML editor · GNU General Public License v3 Read 7 Oct 2026 · jetuml.org

Every JetUML plan and price →

Strong points and limits

Strong points

  • Free plan and open-source GPL v3+ license
  • Supports five UML diagram types
  • Automatic association-edge layout
  • Exports SVG, PNG, and JPEG
  • Documented JSON format

Limits

  • Larger diagrams can reduce performance
  • Java and JavaFX required for OS-independent archive
  • Desktop application only

Who it suits

It suits people who want a focused desktop UML tool for quickly sketching software ideas on Windows, macOS, or Linux. Its open JSON format also suits workflows that need documented diagram files.

Verdict

JetUML covers core UML sketching with automatic edge layout, validation, and several export options. Its free license and documented JSON storage are useful, though larger diagrams may affect performance.

Where Specifiction places it

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