Everyone talks about collaborative data structures like they're the complete solution for real-time apps. They're not. CRDTs handle the conflict resolution brilliantly, but that's only one piece of what you need to build. You'll still be writing code for presence, UI components, permissions, and dozens of other features before users can actually collaborate as well as operating the real-time infrastructure to host the solution. The question is which library gets you closest to a working product with the least custom development.

TLDR:

• CRDTs solve real-time sync by letting users edit locally then merge changes automatically

• Automerge requires building your own UI, presence, and collaboration features

• Most libraries need months of dev work; Velt ships collaborative features in days

• Velt offers enterprise security, scales to millions of users, and includes AI features

What are CRDT Libraries?

CRDTs are specialized data structures built for distributed systems where multiple users edit the same data at once. The challenge: keeping changes in sync without losing information or creating conflicts.

Traditional approaches use a central server to coordinate every change, creating bottlenecks and failing when users go offline. CRDTs work differently. Each user makes changes to their local copy, then those changes merge automatically using mathematical rules that guarantee consistency. Think about this way: instead of preventing conflicts, CRDTs are designed so conflicts can't happen. Each operation is commutative, so order doesn't matter. Whether User A's edit arrives before or after User B's, the final result is identical across all devices. This makes CRDTs valuable for real-time collaborative apps like Google Docs, multiplayer games, or any software where users work together. They also power offline-first experiences where apps keep working without internet, then sync when connection returns.

CRDT libraries package these algorithms into ready-to-use code. Instead of implementing complex distributed systems logic from scratch, you can use battle-tested implementations that handle the synchronization math.

How We Ranked CRDT Libraries

We ranked available CRDT libraries using publicly available information instead of conducting our own performance tests. Our evaluation considers several factors that matter when choosing a CRDT implementation for production use:

• Performance characteristics. We looked at these from independent benchmarks and research papers. Some libraries show dramatic speed differences in specific scenarios, with documented improvements exceeding 5000x in certain operations.

• Implementation maturity. We assessed implementation maturity by looking at how long the library has been in production, its maintenance activity, and real-world deployment examples.

• Developer experience. We looked at documentation quality, API design, integration complexity, and how quickly you can get started.

• Ecosystem support. We also assessed community size, available integrations, and whether the library works across different languages and frameworks.

Best Overall CRDT Libraries: Velt

Most CRDT libraries provide data structures and sync algorithms. Velt delivers a collaboration stack built on CRDT foundations, and leveraging Yjs behind the scenes, that handles data synchronization and the user-facing collaborative experience.

Key Features

Velt includes a number of key features for collaborative applications:

• Includes UI layer, presence system, permissions, notifications, and communication features out-of-the-box

• Add live cursors, contextual comments, and real-time editing with a few lines of code

• Resolves conflicts while pre-built components manage the interface

• Provides a fully managed unified architecture with infrastructure capable of scaling to millions of monthly active users

• Integration takes days, and you get enterprise features like end-to-end encryption, audit logs, and self-hosting options.

This matters when you need collaboration that scales with enterprise security requirements. You get a complete solution Instead of low-level primitives that require a lot of engineering investment to productization.

Yjs

Yjs is a modular framework for building collaborative applications that exposes its internal data structure as shared types, with changes automatically distributed to other peers and merged without conflicts.

Key Features

Yjs includes a number of key features for collaborative applications:

• Support for offline editing, version snapshots, undo/redo and shared cursors with unlimited scalability

• Multiple modules for different editors, communication protocols, and databases

• Network-agnostic architecture supporting peer-to-peer connections

The Downsides

Yjs requires bundle size overhead through WebAssembly generation, making debugging more challenging and potentially impacting browser performance. It requires you to bring your own realtime infrastructure. You'll need to implement your own UI components, user presence indicators, and application-level features.

The Bottom Line

Yjs offers powerful CRDT capabilities for text collaboration but requires substantial development effort to create production-ready collaborative applications. It's good for teams building text editors or document collaboration who need granular control over synchronization protocols and don't mind handling infrastructure complexity.

Automerge

Automerge is a CRDT implementation with a JSON data model, built in Rust with JavaScript bindings through WebAssembly. Network communication happens via automerge-repo, a separate module that handles synchronization between peers.

Key Features

Automerge includes a number of key features for collaborative applications:

• RGA algorithm implementation designed for collaborative editing

• Multi-language support through Rust core with bindings for JavaScript, Python, and other languages

• JSON-like document structure for familiar data manipulation

The Downsides

Automerge historically suffered from performance issues, with some operations taking nearly 5 minutes compared to optimized implementations completing identical work in 56 milliseconds. While version 2.0 addressed many bottlenecks, you still need to build collaboration UI, handle networking infrastructure, and manage application state separately.

The Bottom Line

Automerge provides capable CRDT functionality for JSON documents but demands development work to create complete collaborative applications. It requires you to bring your own realtime infrastructure. It's good for applications requiring JSON document collaboration where developers prefer working with familiar object structures.

Loro

Loro is a high-performance CRDT library built with Rust that focuses on memory usage, CPU performance, and loading speed for local-first applications.

Key Features

Loro includes a number of key features for collaborative applications:

• Fugue CRDT algorithm that reduces text editing interleaving anomalies

• APIs for Rust, JavaScript, and Swift

• Data structures including text, lists, maps, trees, and counters

• Version history tracking similar to Git

The Downsides

Loro's API and encoding schema remain experimental. The library advises against production use, and developers must build their own user interfaces, presence systems, and collaboration workflows.

The Bottom Line

Loro delivers strong performance but requires substantial development work and isn't production-ready. It's good for performance-critical applications where developers can invest time building collaboration layers from scratch.

Microsoft Fluid Framework

Microsoft Fluid Framework is a library for building distributed, real-time collaborative web applications using JavaScript or TypeScript.

Key Features

Fluid Framework includes a number of key features for collaborative applications:

• CRDT-inspired distributed data structures with client libraries for shared state

• Ordering service handling message sequencing and minimum sequence number tracking

• Microsoft ecosystem integration with enterprise support

• Hub-and-spoke architecture simplifying convergence through server-side processing

The Downsides

Fluid Framework requires server-side infrastructure for operation transformation, lacks distributed garbage collection, and forces translation between CRDT data structures and application data structures.

The Bottom Line

Fluid Framework offers Microsoft-backed collaboration capabilities but introduces server dependencies that limit flexibility. It's good for Microsoft-centric organizations building document collaboration tools who can use existing Azure infrastructure.

RxDB CRDT Plugin

RxDB writes, stores and replicates CRDTs on NoSQL documents using MongoDB-style update operators processed through the mingo library.

Key Features

RxDB includes a number of key features for collaborative applications:

• Replication protocols for GraphQL, CouchDB, WebSocket, and cloud services

• Both CRDT and custom conflict resolution approaches with automatic merging or manual control

• Storage interface flexibility supporting LocalStorage, IndexedDB, SQLite, and other engines

The Downsides

RxDB's CRDT approach requires representing business logic through static JSON operators, which breaks down when complex user interaction is needed for resolution. Teams must separately implement collaborative UI, real-time presence, and user experience features.

The Bottom Line

This is good for applications needing database-centric CRDT integration where teams prefer NoSQL operations and already use RxDB for local data management.

Liveblocks

Liveblocks is a real-time collaboration library that enables synchronized shared state across clients. It focuses on making multi-user experiences easy to implement in modern web applications, without requiring teams to build their own networking or state-sync infrastructure.

Key Features

Liveblocks includes a number of key features for collaborative applications:

• Uses CRDTs to automatically resolve conflicts between simultaneous edits

• Supports maps, lists, objects, and other shared data types

• Ensures eventual consistency without centralized locking

• Built-in user presence (who’s online, cursors, selections, status)

• Designed for low-latency UI feedback in collaborative apps

The Downsides

Liveblocks does not provide a rich-text editor or document model out of the box and you must integrate it with your own UI logic or a separate editor layer. Compared to libraries like Yjs or Automerge, Liveblocks offers fewer opportunities to customize internal CRDT behavior. Users must also rely on Liveblocks’ managed backend which doesn't make it suitable for fully offline-first or self-hosted-only environments.

The Bottom Line

Liveblocks is best for teams that want collaboration, such as apps requiring real-time UI sync (dashboards, design tools, whiteboards, multiplayer workflows), but don't want to maintain real-time infrastructure.

Feature Comparison Table of CRDT Libraries

Here's how the libraries compare across critical features for real-time collaboration:

FAQ

What is a CRDT library and why would I need one?

A CRDT library provides data structures that automatically merge changes from multiple users without conflicts, using mathematical rules instead of central coordination. You need one if you're building real-time collaborative features like shared documents, multiplayer editing, or offline-first apps where users work simultaneously on the same data.

How do I choose between Yjs and Automerge for my project?

Yjs excels at text collaboration with modular architecture but requires custom UI development. Automerge offers familiar JSON document structures with multi-language support but historically had performance issues. Choose Yjs for text-heavy applications where you can handle infrastructure complexity, or Automerge if you prefer JSON data models and can accept slower operations.

Can I use CRDT libraries for offline-first applications?

Yes, most CRDT libraries support offline editing where users make changes locally, then sync automatically when connection returns. Yjs, Automerge, Loro, and RxDB all handle offline scenarios, though implementation complexity varies. You'll need to build sync logic, conflict UI, and data persistence yourself.

What's the difference between using a CRDT library versus a complete collaboration platform?

CRDT libraries provide low-level data structures and sync algorithms but require you to build UI components, presence systems, permissions, and notifications separately. Complete platforms include these features pre-built, reducing development time from months to days but with less granular control over synchronization protocols. They also include real-time infrastructure and managed hosting.

How long does it take to implement real-time collaboration with CRDT libraries?

Implementation time varies by approach: building from scratch with libraries like Yjs or Automerge typically takes months to handle data sync, UI, presence, and infrastructure. Pre-built collaboration platforms can be integrated in days, though you'll trade customization flexibility for faster deployment.

Final thoughts on CRDT libraries and real-time sync

The right conflict-free replicated data types library depends on what you're building. If you want low-level control and have time to build UI layers, Yjs or Automerge work well. If you need to ship collaborative features fast with enterprise security, Velt gives you the complete stack. Your users get real-time collaboration without months of custom development and you get a product you can launch sooner rather than later.