Operational Transformation
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Operational Transformation (OT) lets multiple users edit the same document at the same time without locking the document or making people wait for each other.
Each user sees their own edit immediately. When another user's edit arrives later, OT adjusts that incoming edit so it still makes sense with the local changes that already happened.
The goal is simple to say and hard to implement: every copy of the document should end up with the same final content.
OT is used for:
- real-time collaborative document editing
- multi-cursor code editors
- shared whiteboards and design tools
- collaborative spreadsheets
- any application where many clients send small, frequent edits to shared state
OT came out of early collaborative-software research in the late 1980s and is still the basis of Google Docs, Etherpad, ShareDB, and many enterprise editors.
This chapter explains why OT exists, how it adjusts concurrent edits, where central servers make the problem easier, and when CRDTs may be a better fit.