It has a flexible extension mechanism with modules, a wide range of existing modules, and you can develop your own modules. Modelio is an open-source collaborative Business, software modeling environment that is used by code developers, business architects, software architects, system architects, workgroups, and analysts.

Build sequence and activity diagrams from plain text.

Export diagrams to eps, pdf, jpg, SVG, and clipboard.

It runs stand-alone or as an Eclipse plug-in on Windows, OS X, and Linux. It is licensed under GPL-3.0 License and written in JavaScript and Java.

UMLet is an open-source UML tool with a simpler user interface for fast UML diagrams. You can add just a small sprinkling of Umple into your code.You can add a little bit of Umple code into an existing Java, PHP, or Ruby system.You can generate top quality code from class diagrams and state diagrams.It is used to draw UML diagrams, embeds models in code, and generate a complete system. Umple is a model-oriented programming technology that adds UML associations and state machines to Java and PHP. Its works online as an eclipse plugin and as a stand-alone command-line Jar. Umple is an open-source modeling tool for software developers and students to make UML in the fastest way in their classroom. Such services don’t have to cost huge amounts of money since open source solutions are available. UML unified modeling language combines techniques from data modeling business, object modeling, component modeling, and can be used throughout the software development lifecycle. UML is an industry-standard, graphical language for specifying, visualizing, and constructing software systems' artifacts. It is an open standard that isn't controlled by any specific vendor this means that you can learn it easily. UML stands for unified modeling language and it is used heavily when designing computer systems large and small, it looks like boxes and arrows with some text.

Use case diagram online