Gaphor

Simple open-source UML and SysML modelling app for Windows, macOS and Linux.

Verified facts: 4 of 4
Alternatives ranked: 4
Approved reviews: 0
Visits sent from here: 0

About Gaphor

Gaphor is a free, open-source modelling application written in Python. It implements a full UML 2 data model, so what you draw is a real model rather than just pictures, and it also supports SysML, RAAML and the C4 model. The design goal is to stay easy to use: model information is shown directly in diagrams, without a maze of hidden property pages, which makes it approachable for students and engineers who find enterprise modelling suites overwhelming. It has a dark mode, can be extended with Python plug-ins, and is used both through its GTK-based interface and from the command line. Installers are available for Windows and macOS, and Linux users can install it from Flatpak or their distribution. It is licensed under Apache 2.0. Gaphor has fewer features than commercial modellers, such as code generation, team repositories or reporting, and a smaller community.

Best for: Students and engineers wanting a free, approachable UML or SysML modeller.

What works

Free and open source
Real UML 2 model, plus SysML and C4
Simple interface without hidden panels
Runs on all three desktop platforms

Why people leave

Fewer features than commercial modellers
No team repository or real-time collaboration
Small community

Top Gaphor alternatives

See all 4

1St
StarUML
A more polished UML tool for a one-time fee.
66.5
2
Visual Paradigm
Full commercial suite with code engineering and team features.
62.6
3
PlantUML
Free UML written as text, easy to keep in the repository.
59.6
4
Archi
Open-source modelling for ArchiMate enterprise architecture instead of UML.
57.2

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Gaphor: common questions

Is Gaphor free?

Yes. Gaphor is free, open-source software.

Is Gaphor open source?

Yes. The source code is on GitHub at gaphor/gaphor.

What platforms does Gaphor run on?

Gaphor is available for Windows, macOS and Linux.

What are the best alternatives to Gaphor?

The highest-ranked Gaphor alternatives right now are StarUML, Visual Paradigm and PlantUML. See the full ranked list for pricing, platforms and verified facts.

See all 4 Gaphor alternatives

Gaphor facts

4 of 4 verified

License: Apache 2.0; Checked Oct 25, 2026gaphor.org(opens source in a new tab); “Open Source No vendor lock-in: Gaphor is written in Python and is 100% Open Source, available under a friendly Apache 2 license .”
Standards: UML, SysML, RAAML; Checked Oct 25, 2026gaphor.org(opens source in a new tab); “Standards Compliant Gaphor implements the UML, SysML, and RAAML OMG standards.”
macOS requirement: macOS 10.15 or newer; Checked Oct 25, 2026gaphor.org(opens source in a new tab); “Gaphor requires macOS 10.15 or newer.”
Linux install: Flatpak recommended; Checked Oct 25, 2026gaphor.org(opens source in a new tab); “Flatpak is the recommended way to install Gaphor in Linux.”