Proton Docs

Proton Docs is a real-time collaborative document editor built into Proton Drive, encrypted end to end on every keystroke — Proton itself cannot read what is being typed, even while several people edit the same document at once. Proton Sheets does the same for spreadsheets, added alongside it.

That puts the pair in the same rare category as CryptPad: zero-knowledge encryption combined with live multi-user editing, an architecture that normally rules out collaboration because a server that cannot read a document cannot merge two people's edits into it. Proton reaches the same result the way CryptPad does, by moving that merge to the client rather than the server.

Proton AG operates from Geneva under Swiss jurisdiction — outside the EU and EEA but covered by an adequacy decision — with Docs and Sheets running on Proton's own European data centres.

Both are included free with any Proton account, including the free plan, with higher storage and collaboration limits on the paid Mail Plus, Drive Plus, Unlimited and Business tiers; the client code is open source, published in Proton's WebClients repository. Sheets imports Excel and Google Sheets files, and Docs sits alongside the rest of Proton's encrypted suite — Mail, Calendar, Pass — for a team already inside that ecosystem.

The gaps are real. There is no presentation app, so the suite covers two of the usual three formats rather than three.

Microsoft format fidelity is not the focus it is at OnlyOffice — Docs and Sheets are built around Proton's own format, with import rather than a promise of exact DOCX or XLSX round-tripping. Proton Sheets launched more recently than Docs and is the less mature of the two. And everything sits inside the Proton account system, so a team not otherwise using Proton is adopting an ecosystem, not just an editor.

What Proton Docs does well

• End-to-end encrypted documents and spreadsheets, even during live co-editing
• Included free with any Proton account, including the free plan
• Swiss company, with Proton's own European data centres
• Open-source client code, published in the WebClients repository
• Sheets imports Excel and Google Sheets files

Where Proton Docs falls short

• No presentation app — documents and spreadsheets only
• Microsoft format fidelity is not the focus, unlike OnlyOffice
• Proton Sheets is newer and less mature than Docs
• Ties a team into the wider Proton account ecosystem

Standout feature. The second zero-knowledge suite in this category: Proton encrypts every keystroke in Docs and Sheets, even during real-time co-editing.