The Pencil Project’s unique mission is to build a free and opensource tool for making diagrams and GUI prototyping that everyone can use.

•  Pencil provides various built-in shapes collection for drawing different types of user interface ranging from desktop to mobile platforms. Starting from 2.0.2, Pencil is shipped with Android and iOS UI stencils pre-installed. This makes it even easier to start protyping apps with a simple installatio
• Popular drawing features are also implemented in Pencil to simplify the drawing operations.
• Starting from 2.0.2 Pencil has even more shape collections included by default. The list of built-in collections now includes general-purpose shapes, flowchart elements, desktop/web UI shapes, Android and iOS GUI shapes.
• There are also many other collections created by the community and are distributed freely on the Internet. You can easily grab a collection and install it into Pencil with a simple drag-and-drop operation.
• Pencil supports outputing the drawing document into different types of formats. You can have your drawing exported as a set of rasterized PNG files or as a web page that can be delivered to the viewers.
•  Pencil also supports exporting documents into popular formats including OpenOffice/LibreOffice text documents, Inkscape SVG and Adobe PDF.
•  Pencil has a clipart browser tool that integrates with OpenClipart.org to let users easily find cliparts by keywords and added them into the drawing by a simple drag-and-drop operation. Clipart listed by the tool are in vector format and hence good for users in scaling to appropriate sizes.