What it does
Pencil Project is a free, open-source desktop tool for drawing interface mockups and flow diagrams. It includes web, desktop, Android and iOS shape collections, page links and exports to PNG, SVG, PDF or web pages. Installers are available for Windows, Mac and Linux.
Stencils, connectors and linked screens
Pencil supplies interface shapes and flowchart elements in the application. Extra stencil collections can be installed by dragging them into Pencil. Diagram connectors join shapes, and an element can link to another page in the same document.
Those page links become hyperlinks in the web export, giving a reviewer a clickable mockup. Other exports include PNG images, SVG vector drawings, PDF and OpenOffice or LibreOffice documents. The integrated OpenClipart browser also lets you find vector artwork by keyword.
Install the desktop build
Open Downloads and choose the Windows installer, macOS disk image or Linux package for your system. The project separates stable releases from nightly development builds; the nightly builds are explicitly marked unstable.
Pencil 4 adds an optional connection through which AI assistants can inspect and edit open documents. Manual drawing with stencils remains part of the application, so you do not need that connection to plan a screen.
Strengths
- Built-in shape collections cover web, desktop and mobile interfaces
- Web exports preserve links between mockup pages
- PNG, SVG, PDF and office-document exports are available
Watch out for
- Nightly development builds are marked unstable
Best for
- Desktop wireframing with reusable stencils
- Clickable mockups that can be exported as web pages
Sources
- Pencil Project (Oct 27, 2026)
- Pencil features (Oct 27, 2026)
- Pencil downloads (Oct 27, 2026)