Notion Rebuilt Collaborative Editing on CRDTs to Stop Losing Concurrent Edits
kevinakwok · x · 2026-09-19
Notion's engineering blog details its rewrite of collaborative editing.
The problem: Before 2025 Notion wasn't truly collaborative. Concurrent edits to the same block used last-write-wins, so the later write fully overwrote the earlier one, and the odds of losing someone's changes grew with the number of collaborators. Separate blocks were stored as separate records so they could be edited concurrently, but same-block conflicts still lost data. Shipping Offline Mode would have made this worse: an offline editor could lose all changes if others edited the same blocks before reconnecting.
The fix: Notion implemented conflict-free replicated data types (CRDTs) for rich-text editing, plus techniques tailored to its block-based document model. The post walks through an example of Emma and Charlie editing the same block, where the server should merge both updates instead of letting the last write win.
Related event: Notion rebuilds editor with CRDTs for real-time collaboration(3 posts)→
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