Pencil Project is a free, open-source GUI prototyping tool for creating mockups and wireframes of desktop and mobile applications. Available for Windows, macOS, and Linux, Pencil provides stencil collections for common interface elements and easy diagram creation.
The stencil system organizes shapes for different platforms and purposes. Built-in collections include desktop widgets for Windows, macOS, and GTK interfaces, mobile patterns for iOS and Android, and common web elements. Additional stencil packs download from community contributors.
Drawing canvas supports multiple pages for complex application designs. Drag and drop placement positions shapes precisely. Alignment guides help create orderly layouts. Rulers and grids provide measurement reference. Page backgrounds set context for designs.
Shape properties including size, position, colors, and text can be modified individually or for multiple selected objects. The property panel provides quick access to common adjustments. Custom properties on some shapes control special behaviors.
Linking between pages creates interactive prototypes. Clickable areas navigate between screens for demonstration purposes. Export to HTML creates browsable prototypes shareable with stakeholders. Additional export formats include PNG, PDF, SVG, and ODT.
Diagram features support flowcharts and process documentation with connector shapes and flowchart symbols. Text labels annotate designs with notes and specifications. Layer management organizes complex pages with elements that can be shown or hidden independently.