tldraw

Yes — tldraw is primarily distributed as an npm package (@tldraw/tldraw) that you embed in a React app to get a fully functional whiteboard with a few lines of code. The custom shape API lets you add domain-specific shapes (e.g., circuit components, UML nodes, music notation) with their own rendering and interaction logic. This is unusual: Excalidraw is more deeply customizable as a fork, but tldraw's package-first model is closer to a SaaS-grade SDK.

tldraw.com is free for personal and open-source use. The source code is published under a custom 'tldraw license' (Watermark Apache 2.0): free for non-commercial use, but commercial use in a product requires either a watermark or a paid commercial license. This is unusual among open-source whiteboards (Excalidraw is MIT) and is a deliberate sustainability choice by the small core team.

tldraw has a more polished UI, smoother performance on huge boards, a cleaner React SDK for embedding, and better mobile/touch support. Excalidraw has the hand-drawn aesthetic, true MIT license (commercial use is unrestricted), and broader ecosystem (Notion, Obsidian, VS Code embeds). For embedding a whiteboard inside a custom SaaS, tldraw is usually the cleaner path; for ad-hoc sketches without licensing concerns, Excalidraw wins.

Yes — tldraw is a PWA that caches the full app on first visit, and your drawings persist locally. Editing, exporting, and importing all work offline. Collaboration rooms (tldraw.com/r/...) require network connectivity. The self-hosted SDK works fully offline by default; you only opt into the collaboration backend if you wire it up.

tldraw is embedded inside products like Cursor (the AI code editor's whiteboard), Roam Research, and a number of design and education startups. The 'Make Real' AI demo (sketch a UI, get working React code from Claude/GPT-4) put tldraw on the map for AI-augmented design tooling in 2024. The core team is small (<10 engineers) and the SDK is the primary commercial vehicle.