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JetUML – a Simple Open Source UML Diagramming Tool

Franco Martinig, Martinig & Associates,

JetUML is a simple desktop open source Unified Modeling Language (UML) tool UML diagramming. The concept of JetUML is to provide the basic support for sketching software design ideas. JetUML currently supports the following UML diagrams: class diagrams, sequence diagrams, state diagrams, object diagrams and use case diagrams. Diagrams can be exported to image file format, and copied to the system clipboard for integration with other tools like word processing software for documentation.

Version tested: JetUML version 2.5 in March-April 2020 on a Window 8 platform.
System requirements: Windows, Mac OS X or Linux with Java Runtime Environment (JRE) 
License & Pricing: Free software, GNU General Public License v3


JetUML requires at least Java 8 to run. On my Windows platform, I just downloaded the jar file and double-clicked on it to open the tool. No specific installation process is required and the size of the application is a just 350Kb


There are very few configuration options in JetUML. You can define the size of the diagram area and whether or not you will show the tools hints and the grid.

Using JetUML

Using JetUML is easy with its simple and intuitive interface. You simply open the type of diagram you want to create and then you position the diagrams items on the screen. You can choose the items to place by either selecting them from the items list visible on the right side of the diagram or with a right-click mouse action. Selecting and moving items is really straightforward and works fine. There are Undo and Redo features to quickly modify changes.

JetUML – a Simple Open Source UML Diagramming Tool

(click on figure to enlarge)

I would however complain that the tools lack some simple productivity features, like automatically opening a naming window in the use case diagram when you place a new item. Having to re-select the item and double-click on it to enter the name is cumbersome if you are drawing a large diagram. It is also not possible to move multiple objects at once, so you have to think where you begin your diagram. You can however move all the items of a diagram with the “Select All” menu option. It would be also nice if some of the basic actions, like saving a diagram could be used from a toolbar with a one-click action. You could however use some of them with keyboard shortcuts. The tools lack also the concept of “project”. So you have to manually create separate folder if you want to group diagrams that describe the same system.

You can export the diagram in different image files format (png, jpg, gif, bmp). In this case, the diagram export is limited to the area where diagram items are placed.

JetUML – a Simple Open Source UML Diagramming Tool


JetUML is a simple open source Unified Modeling Language tool that achieves its goals. It has a low footprint and it supports the basic needs for the main UML diagrams without requiring any training. If you are a software developer that needs an UML tools to develop or record your software design ideas or a computer science professor who want to teach an object oriented approach, then you should explore JetUML.

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This article was originally published in April 2020

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