Automerge

A local-first sync engine: enables collaborative applications with automatic, conflict-free merging of concurrent data changes.

Automerge is a library of data structures (a Conflict-Free Replicated Data Type, or CRDT) engineered for building robust, local-first collaborative applications. It allows multiple users to independently update application state on local devices, even while offline, then automatically merges those concurrent changes without requiring a central server. This functionality is similar to Git, but for complex data structures (not just plain text). The core implementation is in Rust, with bindings for JavaScript (via WebAssembly) and C, and the recent Automerge 3.0 release achieved a 10x reduction in memory usage: a critical performance gain for documents with long histories.

https://automerge.org/