Angular Change Detection

How Angular detects and propagates state changes to the UI.

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Angular Change Detection

Change detection is the process by which Angular synchronizes the state of the application with the user interface.

Key concepts:

  • Zone.js: The legacy library that monkey-patches browser APIs. Modern Angular (v22+) is moving towards a Zoneless architecture by default.
  • ChangeDetectionStrategy.OnPush: As of Angular 22, OnPush is the default for all new components, leveraging Signals for precise UI updates.
  • Zoneless Angular: The standard approach in v22, removing the dependency on Zone.js for better performance and smaller bundles.
  • Signal-based Reactivity: The core engine driving change detection in v22, allowing Angular to track exactly what needs to change without traversing the entire component tree.