tldraw

tldraw is an SDK for building infinite canvas applications in React. It supplies a complete canvas engine that serves as the foundation for whiteboards, diagramming tools, design editors and other canvas products, and it ships a default whiteboarding tool set that you can use as is or replace with your own primitives.

Out of the box it offers pressure-sensitive drawing, geometric shapes, rich text, arrows with snapping, image and video support and image export. Developers can extend it with their own shapes, tools, bindings, interface components, side effects and event hooks, and can drive the canvas at runtime through the Editor API. Multiplayer collaboration is available through a self-hostable sync package, there are canvas primitives for building with LLMs, and the DOM-based rendering can embed websites such as YouTube, Figma and GitHub. It works in desktop and touch browsers.

Starter kits provide the custom shapes, tools and interface for common application types, and each kit is MIT licensed. The SDK itself is under tldraw's own license rather than a standard open-source one, so review the terms before shipping it in a commercial product.