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derbyjs/derby

★ 4,710TypeScriptAudience · developerComplexity · 4/5LicenseSetup · hard

TLDR

A Node.js web framework that keeps data automatically synced across all connected browsers and the server in real time, with offline support built in.

Mindmap

mindmap
  root((Derby))
    What it does
      Real-time data sync
      Server-side rendering
      Offline support
    Tech stack
      Node.js
      TypeScript
      Racer sync engine
    Use cases
      Collaborative apps
      Real-time editors
      Offline-first apps
    Who uses it
      Web developers
      Full-stack teams
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Code map

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Things people build with this

USE CASE 1

Build a collaborative real-time app where multiple users edit shared data and see each other's changes instantly.

USE CASE 2

Create a web app that loads fast because pages are pre-rendered on the server and then stay live in the browser.

USE CASE 3

Build an offline-capable web app that syncs data automatically and resolves conflicts when the user reconnects.

Tech stack

TypeScriptNode.jsJavaScript

Getting it running

Difficulty · hard Time to first run · 1h+

Requires understanding Racer's data model and subscription system, documentation lives in a separate repository.

Free to use, modify, and distribute for any purpose, including commercial projects, as long as you keep the copyright notice.

In plain English

Derby is a framework for building web applications where multiple people can work on the same data at the same time, with changes appearing instantly for everyone involved. It runs on both the server (in Node.js) and inside the browser, which means the same code handles both sides of the application. At the heart of Derby is a data synchronization system called Racer. Racer keeps data in sync across browsers, servers, and a database automatically. Rather than requiring you to set up dedicated communication channels, models simply subscribe to specific objects and receive updates whenever those objects change. Racer also handles the case where a user goes offline, including conflict resolution when they reconnect. Because Derby renders its templates on the server first, pages load immediately and search engines can read their content. Once the page loads in the browser, templates stay connected to the underlying data through bindings: when the data changes, the view updates on its own, and when the user interacts with the view, the data updates in turn. The project describes the combination of these features as making it possible to build applications that load as fast as a search engine, feel as interactive as a document editor, and continue working when offline. The README is brief and points to separate documentation and examples for more detail. Derby is an open-source project under the MIT license. It has been in development since 2011 and is maintained by the derbyjs team.

Copy-paste prompts

Prompt 1
How do I set up a Derby.js app with Racer data sync so two browser tabs see each other's changes in real time?
Prompt 2
Show me how to define a Derby model that subscribes to a list of items and displays them in a template that updates automatically.
Prompt 3
How does Derby handle conflict resolution when a user makes changes while offline and then reconnects to the server?
Prompt 4
Walk me through building a simple collaborative to-do list with Derby where all users see additions and completions instantly.
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