Excalidraw
excalidraw.com
Virtual whiteboard for hand-drawn style diagrams and collaboration.
Excalidraw is an open-source virtual whiteboard that creates diagrams with a hand-drawn aesthetic. It supports real-time collaboration, a built-in shape library, and exports to SVG and PNG. No account required.
Why it is useful
The hand-drawn style makes technical diagrams feel approachable instead of clinical. Zero-friction start with no login means you can share a link and be collaborating in seconds.