Simon Willison's Weblog: crdt

Merge State Visualizer

2026-03-22T18:57:32+00:00

Bram Cohen wrote about his coherent vision for the future of version control using CRDTs, illustrated by 470 lines of Python.

I fed that Python (minus comments) into Claude and asked for an explanation, then had it use Pyodide to build me an interactive UI for seeing how the algorithms work.

Tags: bram-cohen, vcs, crdt, pyodide

CRDT: Text Buffer

2024-05-20T21:19:07+00:00

CRDT: Text Buffer

Delightfully short and clear explanation of the CRDT approach to collaborative text editing by Evan Wallace (of Figma and esbuild fame), including a neat interactive demonstration of how the algorithm works even when the network connection between peers is temporarily paused.

Via Lobste.rs

Tags: crdt, explorables

Making CRDTs 98% more efficient

2023-10-17T17:15:15+00:00

Making CRDTs 98% more efficient

Outstanding piece of explanatory writing by Jake Lazaroff showing how he reduced the transmitted state of his pixel art CRDT implementation from 643KB to 15KB using a progression of tricks, each of which is meticulously explained and accompanied by an interactive demo.

Via Hacker News

Tags: crdt

An Interactive Intro to CRDTs

2023-10-04T15:10:52+00:00

An Interactive Intro to CRDTs

Superb interactive essay by Jake Lazaroff, providing a very clear explanation of how the fundamental mechanisms behind CRDTs (Conflict-free Replicated Data Types) work. The interactive explanatory demos are very neatly designed and a lot of fun to play with.

Via Hacker News

Tags: crdt, explorables

Building a BFT JSON CRDT

2022-11-21T19:56:50+00:00

Building a BFT JSON CRDT

Jacky Zhao describes their project to build a CRDT library for JSON data in Rust, and includes a thorough explanation of what CRDTs are and how they work. “I write this blog post mostly as a note to my past self, distilling a lot of what I’ve learned since into a blog post I wish I had read before going in”—the best kind of blog post!

Via Hacker News

Tags: json, rust, crdt

Notes on Notes.app

2021-12-09T22:39:26+00:00

Notes on Notes.app

Apple's Notes app keeps its data in a SQLite database at ~/Library/Group\ Containers/group.com.apple.notes/NoteStore.sqlite - but it's pretty difficult to extract data from. It turns out the note text is stored as a gzipped protocol buffers object in the ZICNOTEDATA.ZDATA column. Steve Dunham did the hard work of figuring out how it all works - the complexity stems from Apple's use of CRDT's to support seamless multiple edits from different devices.

Tags: apple, sqlite, crdt, dogsheep

I was wrong. CRDTs are the future

2020-09-28T21:03:57+00:00

I was wrong. CRDTs are the future

Joseph Gentle has been working on collaborative editors since being a developer on Google Wave back in 2010, later building ShareJS. He’s used Operational Transforms throughout, due to their performance and memory benefits over CRDTs (Conflict-free replicated data types)—but the latest work in that space from Martin Kleppmann and other researchers has seen him finally switch allegiance to these newer algorithms. As a long-time fan of collaborative editing (ever since the Hydra/SubEthaEdit days) I thoroughly enjoyed this as an update on how things have evolved over the past decade.

Via Hacker News

Tags: algorithms, collaboration, crdt, martin-kleppmann

The Xi Text Engine CRDT

2017-10-13T22:32:20+00:00

The Xi Text Engine CRDT

Xi is “a modern editor with a backend written in Rust”—an open-source text editor project from Google built on some very interesting computer science (Conflict-free Replicated Data Types). It’s a native editor with server-backed synchronization as a first-class concept.

Via xi-editor

Tags: editor, google, rust, crdt