rxjs 9 beta

RxJS 9 extends the web-platform Observable with exact Symbol-keyed operators and factories, plus a small set of intentional RxJS primitives. It uses a native Observable when one exists and otherwise initializes the separately published @rxjs/observable-polyfill fallback.

This is prerelease software. Install the current beta with:

npm install rxjs@next

RxJS 7 remains npm's latest line during the beta and continues to be maintained.

Why version 9?

Work on RxJS 8 began years ago and paused while Web Platform Observables were finalized. RxJS 9 is a new platform-based generation, not a release of that paused implementation. The version communicates that architectural break and prevents the old RxJS 8 work from being mistaken for this product.

Use an operator

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

const source = new ColdObservable<number>((subscriber) => {
  subscriber.next(1);
  subscriber.next(2);
  subscriber.next(3);
  subscriber.complete();
});

source[pipe](
  (values) => values[map]((value) => value * 2),
  (values) => values[scan]((total, value) => total + value, 0)
).subscribe(console.log); // 2, 6, 12

Each operator subpath exports its exact Symbol and installs only that capability. Importing the root does not install the operator catalog.

Choose the lifecycle deliberately

new Observable(initializer) follows the platform contract. Concurrent observers share the active producer, the last observer leaving tears it down, and a later observer starts it again.

new ColdObservable(initializer) creates one producer for every direct subscription. Use it when producer-per-subscription behavior is part of the application contract rather than assuming all Observables are cold.

Cancellation uses AbortSignal:

const controller = new AbortController();
source.subscribe(console.log, { signal: controller.signal });
controller.abort();

ESM and Node require()

The package publishes one ESM implementation. Browser, Webpack, ESM import, and Node's require(esm) bridge resolve the same files and exact Symbols.

const { ColdObservable } = require('rxjs');
const { map } = require('rxjs/map');

The bridge requires Node 22.13 or newer. It is not a CommonJS build and does not support legacy CommonJS resolvers.

Documentation

• Security assurance and release verification
• API and import guide
• Migrate from RxJS 7
• Unsupported RxJS 7 surfaces
• Migration evidence ledger
• Release environments and budgets
• Beta.0 approval record
• Contributing to the package

The package export map in package.json is authoritative for available public subpaths.