Comparison of Free UML Tools

There is a lot of different UML modelling software to choose from. Here, I will create a short overview over the most common free uml tools. This list is not meant as an exaustive review, but more to give you an idea what each of the tools can to so you have an easier time choosing the uml tool that is best for you.

Gaphor

Difficulty to use: 1/5

Systems: Linux, Mac OS X, Windows

Exports to: SVG, PNG, PDF, XMI

Website: http://gaphor.sourceforge.net

Supports:

Class Diagram
Component Diagram
Use Case Diagram
Activity Diagram
State Diagram
Profile Diagram

Notes:

to add a new Attribute to a Class, press Ctrl + e
to create an aggregate or comosite: create an association, select it, press Ctrl + e

	simple, easy to use UML tool
	Exports to XMI
	no code generation from UML
	no code to UML

Summary:
simple, light weight uml tool which is good to quickly draw up a uml diagram

ArgoUML

Difficulty to use: 3/5

Systems: platform independent (Java Runtime Environment)

Exports to: XMI, PNG, SVG, GIF, JPEG, EPS, PS

Website: http://argouml.tigris.org/

Supports:

Class Diagram
Use Case Diagram
Sequence Diagram
Collaboration Diagram
State Diagram
Activity Diagram
Deployment Diagram

Code generation for: C++, C#, Java, PHP4, PHP5, SQL

code reverse engineering (Code to UML): Java, C++, C#, IDL (including relationships)

	Code generation from UML
	Code to UML
	Exports to XMI
	UI a bit crowded, harder for beginners

Summary:
Uml software with quite a bit of options and functionality. These might overpower a beginner, but if you do have a moment to look through all of it, you get a powerfull free uml modelling tool.

Dia

Difficulty to use: 2/5

Systems: Linux, Mac OS, Windows

Exports to: XMI, PNG, PDF, SVG, JPEG (among others)

Website: https://wiki.gnome.org/Apps/Dia

	Exports to XMI
	can create a LOT of different diagram types
	for many diagrams, not all elements exist
	no code generation from UML
	no code to UML

Summary:
light weight general purpose diagram tool. I would not recomment it for any serious work/documentation, but it is quite usefull to create any needed diagram quick and dirty.

Violet UML Editor

Difficulty to use: 2/5

Systems: platform independent (Java Runtime Environment)

Exports to: PNG, JPEG, HTML

Website: http://alexdp.free.fr/violetumleditor/page.php

Supports:

Class Diagram
Use Case Diagram
Activity Diagram
State Diagram
Object Diagram
Sequence Diagram

code reverse engineering (Code to UML): Java (only single classes)

Notes:

Existing classes cannot be moved to new Package and classes added to a package cannot be moved outside of it by drag’n’drop. But you can cut and paste them.
When creating dependencies for a class inside a package: Click inside the class, not the border of it, otherwise the dependency will attach itself to the package, not the class
Dependencies cannot me moved after creation
When double-clicking on a dependency inside a package, the package properties are opened. Right-click on the dependency to select its properties

	also works as eclipse plugin
	no code generation from UML

Summary:
light weight uml tool, which is sometimes a bit akward to use.

UMLet

Difficulty to use: 4/5

Systems: platform independent (Java Runtime Environment)

Exports to: PNG, PDF, SVG, JPEG, EPS, BMP

Website: http://www.umlet.com/

Supports:

Class Diagram
Use Case Diagram
Interaction Diagram
State Diagram
Activity Diagram
Deployment Diagram
Context Diagram

code reverse engineering (Code to UML): Java (only classes, no relationships)

Notes:

attributes, operations, etc. cannot be changed via GUI, but via a custom Properties file (which may be edited directly in the GUI, but you do need to learn the layout of this file, which means reading the documentation)

	also works as eclipse plugin
	no code generation from UML
	not very user friendly

Summary:
This tool offers no functionality which could not also be found in most other UML tools. But it is more difficult to use, so I would not personally recommend it.

yEd

Difficulty to use: 2/5

Systems: platform independent (Java Runtime Environment)

Exports to: BMP, EPS, GIF, HTML, JPG, PDF, PNG, SVG, SWF

Website: http://www.yworks.com/en/products_yed_about.html

Supports:

Class Diagram
Use Case Diagram

Notes:

supports a lot of different diagrams, but only class and use case as far as uml is concerned
class diagram elements are quite limited. There is no option for interfaces, abstract classes or similar

	simple, easy to use UML tool
	no code generation from UML
	no code to UML
	very limited

Summary:
It is a nice tool, but as far as UML is concerned, it is too limited for me

Papyrus

Difficulty to use: 5/5

Systems: platform independent (Java Runtime Environment)

Exports to: ?

Website: http://www.eclipse.org/papyrus/updates/index.php

Supports:

Class Diagram
Activity Diagram
Communication Diagram
Component Diagram
Composite Structure Diagram
Deployment Diagram
Interaction Overview Diagram
Package Diagram
Sequence Diagram
Use Case Diagram
State Diagram
Timing Diagram

Code generation for: C++, Java (at least theoreticly. It is deprecated and I could not get it to work for me)

Notes:

I could not figure out how to use a lot of the functionality. Among others, I was not able to display fields inside the diagram, create a diagram from existing code, generate code from an uml diagram, or even export a diagram.

	Code to UML
	only eclipse plugin (no stand-alone version)
	code generator is deprecated
	not very user friendly

Summary:
I found Papyrus extremly unintuitive to use, but your mileage may vary. An extensive 60 page PDF documentation exists, so if you have the time and energy you might be able to achive quite a bit with Papyrus.

Modelio

Difficulty to use: 3/5

Systems: Linux, Windows, Mac OS X

Exports to: XMI, PNG, BMP, JPG, GIF

Website: http://www.modelio.org

Supports:

Class Diagram
Component Diagram
Instance Diagram
Activity Diagram
Communication Diagram
Composite Diagram
Use Case Diagram
Object Diagram
Sequence Diagram
State Diagram
Use Case Diagram

Code generation for: Java, Paid Content

	Exports to XMI
	quite big (compressed 175 MB)
	no code to UML

Summary:
Too heavy weight for what you get (probably because it is based on Eclipse), some functionality (eg Code generation) is not free.

Further free UML Modelling Software

NClass

Website: http://nclass.sourceforge.net/

Overview:

quite incomplete (Wikipedia says that even Undo is still missing)
only class diagram
code generation from UML

Note:
could not test, as it depends on the Microsoft .Net Framework

StarUML

Website: http://staruml.sourceforge.net/‎

Overview:

unmaintained since 2005 (but a new Fork called WhiteStarUML exists)

Note:
could not test, as it only runs on windows

Umbrello

Website: http://umbrello.kde.org/

Note:
could not test, because kde wouldn’t install

What’s the best free UML tool?

So what is the best free uml tool? It really depends on what you want to do with it.

Personally, for throw-away diagrams I use Dia. For small(ish) UML diagrams I would recommend Gaphor, and if you need a more complex UML tool with a lot of functionality, I would recommend ArgoUML.

As always, you might feel differently, and it cannot hurt to try out more than one tool.

If you know of any more UML modelling software or have an option on one of the uml tools presented here, please feel free to share it in the comments.