2cross

2cross is an open-source software framework that provides real-time, cross-platform data synchronization across devices and services. It aims to unify data models and enable seamless collaboration by prioritizing offline-first operation and conflict-free merging through a CRDT-based synchronization core. The project is designed to be language-agnostic, with modular adapters that connect to various storage backends and client platforms.

2cross was conceived by a community of developers in the early 2020s and reached its first stable release in 2021. Development is community-driven, with public repositories and permissive licensing that encourage collaboration and transparency. The framework emphasizes interoperability and security, aiming to run across web, mobile, and desktop environments.

At its core, 2cross consists of a CRDT engine, a transport layer, and a set of adapters. The CRDT engine manages state and ensures eventual consistency. The transport layer supports multiple protocols, including WebSocket, HTTP long polling, and peer-to-peer channels. Adapters enable integration with databases, mobile platforms, and web runtimes. The framework emphasizes pluggable conflict-resolution policies and data-model mapping to accommodate diverse applications.

Key features include real-time synchronization, offline support, deterministic conflict resolution, multi-device synchronization, and cross-language SDKs for JavaScript, Python, and Swift. Common use cases include collaborative document editing, shared task boards, offline-first mobile apps, and multi-device data continuity for IoT dashboards.

2cross is maintained by an international community of volunteers and companies. It employs an open-source license and encourages contributions through public issue trackers, pull requests, and documentation improvements.