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