Zoneless change detection and render lifecycle

Zoneless is the default in Angular 21 and later. Angular refreshes views from known notifications instead of patching every browser async API through Zone.js.

Notifications

Angular learns a view may need work when a template-read signal changes, an input is set, a listener runs, AsyncPipe emits, a marked view is attached, or code calls markForCheck.

Code that mutates an untracked plain field after a timer may not update the view. Make state visible through signals, inputs, or supported notification.

OnPush

OnPush remains useful because it encourages explicit data flow and zoneless- compatible components. It is not a magic performance flag and does not repair mutated inputs.

Lifecycle

Use constructor/field initialization for dependency setup, ngOnInit for input- dependent initialization, and ngOnDestroy or DestroyRef for cleanup. Avoid work in frequently invoked checked hooks.

Render callbacks

afterNextRender and afterEveryRender coordinate DOM-dependent work after rendering. Keep browser-only APIs guarded for SSR. Use cleanup when the callback owns observers or third-party instances.

Expression changed errors

These errors expose a state mutation during a check that made the rendered result unstable. Fix ownership and timing rather than adding arbitrary setTimeout.

Performance model

Signals reduce the affected graph; component boundaries, stable identity, deferred code, DOM size, JavaScript work, and network latency still matter. Measure with browser performance tools and Angular DevTools.

Feynman check

Zoneless does not mean “Angular never checks.” It means Angular checks in response to explicit notifications. Name the notification for every state update on one page.