Virtual whiteboard for sketching hand-drawn like diagrams

Excalidraw is a free, open-source virtual whiteboard that lets users sketch diagrams with a hand-drawn, rough-pencil aesthetic — intentionally avoiding the sterile, perfect-line look of tools like Visio or Lucidchart. It runs entirely in the browser (no account needed) and is popular among developers, designers, and remote teams for quick wireframes, architecture diagrams, or brainstorming. The project is maintained by a small team led by former Facebook engineer Vjeux (Christopher Chedeau) and fully available on GitHub, meaning anyone can self-host or contribute. Its "hand-drawn" style, powered by the Rough.js library, makes sketches feel informal and iterative — useful for early-stage design discussions where polish would be misleading.