Excalidraw

Excalidraw is an open-source virtual whiteboard that allows users to sketch diagrams and collaborate in real-time. It offers a free version with full editor functions, including an infinite canvas, unlimited collaborators, and export options to PNG, SVG, or saved files. Integrations with Notion, Obsidian, and other tools are also available. The free version stores one infinite scene in your browser's storage, which can be cleared, so it's recommended to save your work to your own disk. Excalidraw is accessible directly in your browser without the need for an account or payment.

Excalidraw+ is the paid version, priced at $6 per user per month when billed annually, or $7 per user per month when billed monthly. It includes all features of the free version, plus unlimited scenes and folders saved on Excalidraw's cloud, access management, sharing with edit or view rights, read-only links and embeds, voice hangouts and screen sharing, presentations with PDF and PPTX export, extended AI features, and team management. A 14-day free trial is available for new users. Excalidraw+ is also accessible via web browsers.

Platforms: Excalidraw is accessible via web browsers, with no official apps for other platforms.