Change detection

The ng-select component implements OnPush change detection, which means the dirty checking checks for immutable data types. That means if you do object mutations like:

this.items.push({ id: 1, name: 'New item' });

the component will not detect a change. Instead you need to do:

this.items = [...this.items, { id: 1, name: 'New item' }];

This will cause the component to detect the change and update. Some might have concerns that this is a pricey operation; however, it is much more performant than running ngDoCheck and constantly diffing the array.

Zoneless change detection

@ng-select/ng-select and @ng-select/ng-option-highlight fully support zoneless change detection — the default for new Angular apps since v21. No setup is required: the libraries do not depend on zone.js (it is not in their dependency graphs) and work identically whether your app is zoneless or still uses zone.js. Both modes are covered by the unit-test suite in CI, and this docs site runs zoneless.