Two people, one document, no lock-outs and no emailed copies. How the shared session really works - and where its edges are.
The moment that sells this whole setup is two people editing one document at the same time - no file locks, no version chaos by email. This page explains what is really happening behind that moment: the live session, the two co-editing modes, and the exact point where changes become a saved file.
Both users open the same document in Nextcloud. Instead of locking the file (the old shared-folder way), OnlyOffice puts both into one editing session run by the Docs server. Each person sees the other's cursor as a coloured flag with a name, and text appears as the other person types it. There is still one file in Nextcloud - the session is a shared workspace on top of it.
Changes during the session live on the Docs server. When the last person closes the document, the Docs server assembles the final file and sends it back to Nextcloud through the callback. That is why a stable Docs server matters: it is holding the live session.
OnlyOffice has two co-editing behaviours, and the connector settings in Nextcloud let the admin choose the default:
Users can also switch their own view of the mode inside the editor's collaboration settings in many setups, but the admin default decides what the team gets.
Two people typing in the same sentence at the same second can still tangle each other's words - the software merges character by character, it does not read minds. Teams develop the simple habit of working in different sections, which the visible cursors make easy.
Also know: tracked changes and comments work during co-editing, chat sits inside the editor, and version history in Nextcloud records the file states after sessions close - not every keystroke. If the Docs server crashes mid-session, work since the last assembled save can be lost; the recovery is the Docs server's session cache, which is one more reason the backup guide says to back up during quiet hours.
Watch the video's live demo of a document being opened and edited - that session behaviour is exactly what this page explains.
Watch Full VideoTechnically yes - the editor merges changes character by character and shows both cursors live. In practice, two people typing in the same sentence at the same second can garble each other's words. Teams naturally split by section, which the visible cursors make easy.
The Docs server holds the changes during the session and writes the finished file back to Nextcloud when the last editor closes the document (or through its save cycle). Nextcloud version history then keeps that saved state, not every keystroke.
Fast mode shows everyone's typing live, Google Docs style. Strict mode locks the paragraph being edited and reveals changes when that person saves, which suits formal review. The admin sets the default in the Nextcloud connector settings.