Frequently Asked Questions


On which platforms does UMLet run?

UMLet runs on any Java platform, e.g., Windows, Linux, and macOS.

How to start UMLet (stand-alone)?

Download the UMLet zip file, unzip it, and start "umlet.jar" with a double-click.

I still have problems starting UMLet...

First, make sure that Java is installed; you can check your Java version by typing "java -version" on your command line.

Also make sure that jar-files are associated with Java if you want to start them with a double-click. Alternatively, you can start UMLet from the command line: cd to the UMLet directory and type "java -jar umlet.jar". (There is also a startup shell script for Linux, as well as a Windows exe wrapper.)

UMLet uses your home folder for configs; if you still experience problem, you might now have the required write permissions there.

How to start UMLet as Eclipse-Plugin?

Usually, you should be able to install UMLet via the Eclipse marketplace. In case of firewall issues, you can download the plugin, unzip it, ans use "Install Software > Add > Local". More info is available on our tech wiki.


How to add elements to the diagram?

Double-click on any element in the palette; it will appear in the upper left corner of the main diagram window.

How to duplicate elements on the diagram?

Double-click on an element to duplicate it. Alternatively, use copy/paste or Ctrl+C/Ctrl+V.

How to select multiple elements?

Hold Ctrl to select multiple elements.

How to lasso-select multiple elements?

Hold Ctrl, press the left mouse button, and select a rectangle containing the desired elements.

How to change UML elements?

Select an element and modify its attributes in the lower right text panel. Each element type has a simple markup language, eg, the text "/ClassName/" causes "ClassName" to become italic. The markup languages are best explored via the sample UML elements in the palettes.

How to enter comments in a UML element description?

UMLet supports C++-style comments---starting a line with "//", eg, "//my comment..", will let UMLet ignore that markup line.

How to change the color of UML elements?

Right-click on an element and select its background or foreground color via the context menu. Alternatively, just type the name of the color in the element description, eg, "bg=black", or "fg=red".

How to create UML relations?

Double-click on a relation and then drag its end points to the borders of UML elements; they will stick there.

How to edit the relations?

Many UML tools make it time-consuming to change the type or the direction of a relation. In UMLet, simply modify the linetype, ie, by changing the line "lt=" in the element description. For example, change "lt=<." to "lt=->>" to change the direction, the arrow type, and the line's dots at the same time.

How to label relations?

  • Edit the name of a relation in the relation's description.
  • Role names can be specified using "r1=" or "r2=".
  • For multiplicities use "m1=" or "m2=".
  • Qualifiers are done with "q1=" or "q2=".

How to create sequence diagrams?

Change the current palette to "Sequence - all in one". Add the sequence diagram element to the diagram via double-click.

This element's markup language is slightly more complex. The main idea is that each lane has a name and an ID (defined by the string "_name~ID_"). The IDs can then be used to define messages between lanes, eg, "id1->id3".

How to create activity diagrams?

Change the current palette to "Activity - all in one". Add the activity diagram element to the diagram via double-click. Here, TABs in the element description are used to define the activity forks.

How to create my own custom UML element palettes?

Just save a UML diagram in UMLet's palette folder---you can then use it as a palette via the "Palettes" menu. You can also edit the current palette with the menu command "Palettes>Edit Current Palette".


How to copy the current diagram to the clipboard for graphical export, eg, to Word?

Just press Ctrl+C in UMLet, and Ctrl+V in any other application like Word---the whole diagram is copied. (Of course, within UMLet, Ctrl+C behaves in the standard way and just copies the element.)

How to export diagrams to other file formats?

Use the menu command "File>Export as.." to export the diagram to BMP, EPS, GIF, JPG, PDF, PNG, and SVG.

How to use UMLet to (batch-)convert files into other formats like pdf?

Call UMLet from the command line with the following arguments (in this case, to create a jpg-file):
java -jar umlet.jar -action=convert -format=jpg -filename=someinputfile.uxf

You can also batch-convert many files at once via, for example:
java -jar umlet.jar -action=convert -format=pdf -filename=palettes/*.uxf -output=.

Can I create code from UMLet's uxf-files?

UMLet does not provide means to create code from the model, or vice-versa. However, UMLet's uxf file format is a very simple XML format; you can easily parse it with, eg, XSLT, to process the model. (As UMLet is aimed at fast UML sketching, we do not plan to support code creation or round-trip engineering in the future.)

How does UMLet's uxf-format handle relations' stickiness?

The relations' stickyness to elements are defined implicitly, ie, if a relation's end point lies on the border of an element, it is regarded as connected to that element.

How to share my custom UML elements with others?

All the information of a custom element are embedded in its parent diagram -- to share custom elements, just share the uxf-files that contain them.


Where to find additonal infos?

Check out out tech wiki.

Who is developing UMLet?

M. Auer and A. Fuernweger. Former developers: T. Bretterbauer, J. Thöndel, E. Blümelhuber, J. Poelz, L. Meyer, T. Tschurtschenthaler. Version 0.1 was released on January 25, 2001; version 1.0 on June 21, 2002.

How to best contact us for bug reports or feedback?

Best mail us:

2001+ :: GNU GPL 3.0