UMLet is a free and open-source UML tool to draw UML diagrams. It has a simple user interface that lets you draw UML diagrams fast, create new, custom UML elements. Using this tool you can also build sequence and activity diagrams from plain text. Other features include export diagrams to eps, pdf, jpg, svg, and clipboard, share diagrams using Eclipse, etc.
You can the tool as a stand-alone tool or integrate and install within Eclipse as plug-in.The tool supports major operating systems like Microsoft Windows, OS X and Linux.Official link for the tool is:
Standard tool is shipped as a Jar file. You can download the jar file and double click to run the tool (umlet.jar).
The tool is install-free web app, you don’t need to install anything to use the tool.
You can save diagrams in browser storage.
The tool supports many UML diagram types.
You can export .png file format.
You can download the eclipse plugin from the marketplace. To start the plugin, File>>New>>Other from the menu or the context menu; in the subsequent wizard, select “UMLet/Diagram”.
Double-click on elements to add them to the diagram.
Class Diagram using Raptor Tool