Link to their main instance: https://cryptpad.fr/
From the "About" section on their website:
CryptPad provides a full-fledged office suite with all the tools necessary for productive collaboration. Applications include: Rich Text, Spreadsheets, Code/Markdown, Kanban, Slides, Whiteboard and Forms.
End-to-end encrypted
All data on CryptPad is encrypted in the browser. This means no readable data leaves the user's device. Even the service administrators cannot see the content of documents or user data.
Illustration showing two paper shredders destroying and reconstructing a sheet of paper.
Illustration of three people collaborating on a document. They can see the document but the server connecting them only sees random letters and digits.
Private Collaboration
CryptPad is built to enable collaboration with features such as team drives, calendar, and sharing. It synchronizes changes to documents in real time. Because all data is encrypted, the service and its administrators have no way of seeing the content being edited and stored.
Fully open-source
CryptPad is free software. Anyone can host the platform in a personal or professional capacity. The development team offers subscriptions and support contracts for ready-to-use deployments.