pencil

Pencil provides a free, open‑source environment for creating diagrams and graphical user‑interface mockups. It runs on all major desktop operating systems, allowing users to install the application locally and design wireframes, flowcharts, and UI layouts without needing a web service. The tool includes a collection of stencils and templates that cover common UI elements, making it straightforward to assemble prototypes that resemble real applications.

The software targets designers, developers, and product teams who need a lightweight solution for visualizing interface concepts early in the development process. Because it is open source, users can inspect, modify, and extend the code to fit specific workflow requirements, while the free tier ensures unrestricted access to the full feature set.

Pencil’s latest stable release, 3.1.1, focuses on stability improvements and adds new functionality, as documented in the release notes. Ongoing updates are announced through the project news feed, and the project is maintained under an open‑source license that permits free use and redistribution.