RxJS

RxJS is a library for composing asynchronous and event-based programs with Observable values. This repository contains the platform-based next generation of RxJS, planned for release as RxJS 9.

RxJS 9 is prerelease work in development. The planned first beta is 9.0.0-beta.0, but it has not been published to npm yet. The next tag still points to the earlier RxJS 8 prerelease, while RxJS 7 remains the production latest line and continues to be maintained.

Why RxJS 9? What happened to RxJS 8?

RxJS 8 was real work, not a skipped release. Development began years ago and was paused while the Web Platform Observable proposal was finalized. The new implementation is a platform-based generation rather than a continuation of that paused RxJS 8 branch, so it starts at version 9 to make the architectural break unmistakable and avoid presenting the old RxJS 8 work as the released product.

What is different in RxJS 9?

• RxJS uses the native web-platform Observable when one exists and installs a conforming fallback only when needed.
• RxJS operators and factories are exact, module-owned Symbols. They do not add string-named RxJS methods to the platform API.
• Platform Observable behavior and producer-per-subscription behavior are explicit, separate contracts. Use ColdObservable when each direct subscription must create its own producer.
• Cancellation is built on AbortSignal and the platform Subscriber lifecycle.
• Published JavaScript is ESM-only. Current Node can bridge require() to the same ESM files; there is no duplicate CommonJS build.

Preview the RxJS 9 API

The following example shows the planned beta API. Until 9.0.0-beta.0 is published, do not use npm's next tag to install RxJS 9.

import { ColdObservable } from 'rxjs';
import { map } from 'rxjs/map';

const source = new ColdObservable<number>((subscriber) => {
  subscriber.next(1);
  subscriber.next(2);
  subscriber.complete();
});

source[map]((value) => value * 2).subscribe(console.log);

Import the Symbol and call it with bracket syntax. A platform method such as observable.map(project) remains the platform contract; observable[map](project) is the separately versioned RxJS contract.

Packages and documentation

Package	Purpose	Documentation
rxjs	Symbol extensions and intentional RxJS primitives	Package guide · API · RxJS 7 migration
@rxjs/observable-polyfill	Conditional platform Observable fallback	Package guide
@rxjs/test	Implementation-neutral virtual-time and marble testing	Package guide
@rxjs/migrate	Deterministic migration engine and canonical agent Skill	Package guide

Release support, budgets, and exact environment gates are documented in the rxjs package. The irreversible npm publication process is the public secure release runbook. The RxJS 9 security-assurance document explains the release evidence, verification commands, sole-maintainer model, and OpenSSF Scorecard in context. Repository-wide design records live in docs/rxjs-next.

Supported environments

The planned beta supports Node 22.13+ and Node 24 as blocking lanes, with Node 26 in an advisory lane. Current Chrome, Firefox, desktop Safari, Mobile Safari, Deno, Bun, and Webpack 5 are blocking. Every supported consumer receives the same ESM implementation, so Deno and Bun support adds no runtime-specific package or application-bundle code.

Contributing

Requires Node 22.13+ and pnpm 10.34.5. Run commands from the repository root.

pnpm install
pnpm --filter rxjs exec vitest --run src
pnpm --filter rxjs run test:package
pnpm run release:check

Start with the repository contribution guide and the rxjs package contribution guide. The active execution queue is PROJECT_PLAN.md.

The complete source-pinned RxJS 7 corpus intentionally retains reviewed lifecycle and compatibility divergences, so it is migration evidence rather than a blanket RxJS 9 compatibility gate. Focused source, package, runtime, browser, performance, and WPT commands are the release gates.

Community and governance

• Code of Conduct
• Contribution guidelines
• Apache 2.0 License
• Issues
• Discussions