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PlantUML is an open-source tool that uses simple textual descriptions to draw UML diagrams. The generator can be run anywhere within JVM and integrated with various application such as wiki, text editor, IDE, programming language, documentation generator, and others. Mostly based on Graphviz. Can render various diagram syntax such as PlantUML, Dot, and Ditaa.

UMLet is an open-source UML tool with a simple user interface: draw UML diagrams fast, export diagrams to eps, pdf, jpg, svg, and clipboard, share diagrams using Eclipse, and create new, custom UML elements.

Visual Paradigm for UML (VP-UML) is a UML design tool and UML CASE tool designed to aid software development. VP-UML supports key modeling standards such as Unified Modeling Language (UML) 2.4, SysML, ERD, DFD, BPMN 2.0, ArchiMate 2.0, etc. It supports software development teams in requirements capturing, software planning (use case analysis), code engineering, class modeling, data modeling, etc.

Lightweight, powerful, easy to use, UML tool

Graphical modelling open source UML2 tool based on Eclipse environment.

Violet is a UML editor with these benefits: Very easy to learn and use. Draws nice-looking diagrams. Completely free. Cross-platform. Violet is intended for developers, students, teachers, and authors who need to produce simple UML diagrams quickly.

ProcessOn provides an easier way to create diagrams.It's completely FREE OF CHARGE .Drag and drop shapes, icons and other usuful elements in your logic thinking or following your procedure, then optimize your diagrams’ color, style,so everyone even the beginner will become a diagram rockstar just in a minute.ProcessOn also has a diagram library where you can choose tons of shapes and objects then share them through social network. Templates included:-Flowcharts-BPMN-Value chain-ERD-UML-UI/IOS mockups-Org charts-Venn diagrams-MindmapProcessOn is also a professional social network, specially designed for digrammers, designers, consultants, IT engineers.You just can connect with the experts or influences in your professional field, in the meantime, you can rise your personal reputation as well.Here you wont’ miss the lastest trends in one’s specific field.Now we support 5 languages. »

From free light-weight versions which provide Intuitive UML software at no cost; to the most powerful UML Plus software on the market Astah allows your team to communicate clearly and easily across platform. Take your Modeling to the next level with Astah.

NClass is a free tool to easily create UML class diagrams with full C# and Java language support. The user interface is designed to be simple and user-friendly for easy and fast development. Properties, enums, delegates and other language specific elements are fully supported with strict syntactical and semantical verification.

WhiteStarUML is a fork of StarUML with an intent to revive its Delphi code base by updating code to recent Delphi editions, reducing dependence on third party components and fixing bugs and adding new features.

UMLGraph allows the declarative specification and drawing of UML class and sequence diagrams. The current features are part of an ongoing effort aiming to provide support for all types UML diagrams.

A lightweight HTML5/javascript library for UML 2 diagramming.

System Designer uses UML, a standard, to define your model. So you probably already know how to create a model in System Designer even if you have never run it.