Excalidraw

Excalidraw is an open-source virtual whiteboard for sketching diagrams, wireframes, and ideas with a distinctive hand-drawn, low-fidelity style. That aesthetic is deliberate: the sketchy look keeps early-stage work feeling like a draft, which encourages feedback and iteration rather than premature polish. The core editor is completely free, runs in the browser with no signup, and stores drawings locally, making it one of the fastest ways to turn a rough idea into a shareable picture.

Despite its simplicity, Excalidraw is capable. It offers shapes, arrows with binding, freehand drawing, text, images, libraries of reusable components, and export to PNG, SVG, and its own format, plus real-time collaboration where multiple people sketch on the same canvas from a shared link. Frames, laser pointer, and a large community library make it useful for architecture diagrams, user flows, systems design interviews, teaching, and remote brainstorming. Because it is open source, it can be self-hosted and embedded, and the same engine powers integrations in tools across the developer ecosystem.

Excalidraw+ is the optional paid tier that adds cloud storage, workspaces, sharing controls, and team collaboration for people who want persistence and management on top of the free editor. Priced modestly per user with Free and Plus tiers plus custom business options, Excalidraw appeals to engineers, designers, educators, and technical teams who value speed, charm, and openness over the heavier feature sets of Miro, Figma, or Lucidchart.