Angular › Zoneless Change Detection & Zone.js

What does zoneless change detection mean, and how does Angular know when to update the screen without Zone.js?

Intermediate

Answer

Zoneless change detection removes Zone.js entirely and instead relies on more explicit and precise signals, like Angular Signals, to tell Angular exactly which parts of the application changed, so it only needs to update the specific pieces of the screen affected instead of checking everything.

// main.ts
import { bootstrapApplication } from '@angular/platform-browser';
import { provideExperimentalZonelessChangeDetection } from '@angular/core';

bootstrapApplication(AppComponent, {
  providers: [provideExperimentalZonelessChangeDetection()]
});

Real-world example A performance sensitive dashboard app switches to zoneless change detection and signals, and notices faster rendering because Angular now updates only the specific counters that changed instead of scanning the entire component tree after every event.

Common follow-ups: Do you have to rewrite an entire app to switch to zoneless change detection?;What happens to code that still uses regular variables instead of signals in a zoneless app?

Angular Signals;Performance & Lazy Loading