Free whiteboard tools or service for developers

Excalidraw

Excalidraw is a virtual collaborative whiteboard tool that lets you easily sketch diagrams that have a hand-drawn feel to them.

Tags: whiteboard, diagram, drawing

Onlineboard

Browser based online whiteboard app. Allows you to create a whiteboard where others see everything in real-time as you draw it. Dark mode, no login required, multiple colors, export to PNG.

Tags: remote, productivity, whiteboard, blackboard, multiplayer, collaboration