When dynamically creating components using `ViewContainerRef.createComponent` or the standalone `createComponent` function, you can provide an `onError` callback in the options object to handle errors that occur during the rendering or change detection phases. This is the programmatic equivalent of using an `@error` block in templates.

viewContainerRef.createComponent(DynamicComponent, {

onError: (err: Error, details: ErrorDetails) => {

console.error('Component rendering failed:', err);

// Render an alternative UI or log metrics

},

});

NOTE: The `onError` callback only catches errors that occur during the rendering or change detection phases. It does not catch errors that occur during component instantiation (for example, in the constructor). Angular throws construction errors synchronously when you call the API.

IMPORTANT: `@boundary` is in [developer preview](reference/releases#developer-preview).

Angular templates support error boundaries to gracefully handle runtime errors that occur during rendering and change detection.

Error boundaries prevent a single component's failure from crashing the entire application and provide a way to display fallback UI to the user.

The `@boundary` block wraps a section of your template. If any component or directive inside this boundary throws an error during initialization or change detection, the framework catches the error and renders the `@error` block instead.

You can access the caught error by accessing the implicit `$error` variable:

You can attempt to re-render the content of the `@boundary` by calling the implicit `$reset` function in the `@error` block. When called, it resets the boundary state and tries to render the original content again.

You can use `when` clauses to conditionally handle specific types of errors, allowing you to provide different fallback UIs. Angular evaluates this condition when it catches an error.

Order your `@error` blocks from most specific to least specific, as Angular evaluates the `when` clauses in order and uses the first one that evaluates to true. A final `@error` block without a `when` clause acts as a catch-all fallback.

When a boundary catches an error, Angular can still notify the global `ErrorHandler`. You can implement the optional `onViewError` hook in your custom `ErrorHandler` to log these caught errors to your error tracking service.

@Injectable()

export class MyErrorHandler implements ErrorHandler {

handleError(error: any): void {

// Handle uncaught errors

}

onViewError(error: Error, details: ErrorDetails): void {

// Handle errors caught by a @boundary

console.warn('Caught by boundary:', details.boundary);

myErrorTrackingService.log(error);

}

}

IMPORTANT: If an `@error` block itself throws an error, the error propagates to the next outer `@boundary` or Angular treats it as an unhandled application error.

Error handling isn't limited to template syntax. If you are creating components or embedded views dynamically, you can use the `onError` option to handle errors. See the [Handling rendering errors](guide/components/programmatic-rendering#handling-rendering-errors) section in the programmatic rendering guide for more information.

IMPORTANT: The `@boundary` block is in [developer preview](reference/releases#developer-preview). It's ready for you to try, but it may change before it is stable.

The `@boundary` block is a control flow mechanism that lets you intercept and handle rendering errors in templates.

The `@boundary` block encapsulates its content and catches any errors that occur during the initial render or subsequent change detection cycles of its child views. If an error is caught, the framework stops rendering the main view and instead renders the fallback UI provided in the `@error` block.

You can capture the error object by declaring a variable in the `@error` block, for example `@error (let err)`.

You can use multiple `@error` blocks with `when` clauses to conditionally render different fallbacks based on the error type, with a final fallback `@error` block at the end. You can also access a `$reset` function to attempt re-rendering the boundary content.