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Fix the driver behind crashes, sound loss and screen glitchesFind Drivers →Repair Windows errors before they cause bigger problemsFix Now →To add custom service-worker behavior to an Angular app while keeping Angular’s caching and update handling, create a worker that imports ngsw-worker.js first, add your event listeners, copy the custom file into the build output, and register it with provideServiceWorker. Use ngsw-config.json instead when you only need to change which resources Angular caches or how it caches them.
Choose configuration or a custom worker
Start by identifying what needs to change. Angular’s service worker configuration file controls caching for application assets and data requests. Its asset groups and data groups let you define what is cached and the relevant caching behavior.
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- Change cache matching or policy: adjust
ngsw-config.json. - Handle browser events or add behavior outside Angular’s configured caching: extend the Angular worker with a custom script.
- Need advanced caching or offline capabilities: consider native browser APIs. Angular describes its service worker as a basic utility for simple offline support, says it will receive no new features beyond security fixes, and recommends native APIs for more advanced needs. See the Angular service worker overview.
Examples of custom event behavior include reacting to notification clicks or handling background sync. A custom script is not a substitute for checking whether a cache configuration change already solves the problem.
Extend Angular’s worker
Create a custom service worker file in your application source. The key step is importing Angular’s worker before adding custom listeners; this preserves access to Angular’s caching and update functionality. The documented extension pattern is described in Angular’s custom service worker scripts guide.
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importScripts('./ngsw-worker.js');
(() => {
self.addEventListener('notificationclick', event => {
event.waitUntil((async () => {
// Add application-specific notification-click behavior.
})());
});
self.addEventListener('sync', event => {
if (event.tag === 'my-background-sync') {
event.waitUntil((async () => {
// Add application-specific background-sync behavior.
})());
}
});
})();The event names and tag above illustrate where application logic belongs; they do not provide a complete notification or sync implementation. Use event.waitUntil() for asynchronous work so the browser knows the event has work to finish before it can terminate the worker. Handle rejected promises and other failures deliberately. Angular also recommends wrapping custom code in an immediately invoked function expression (IIFE) to limit global-scope pollution.
Include the file in the build and register it
The browser must be able to fetch the custom script from the deployed application. Add it to the build assets in the project’s Angular build configuration, and confirm that its output location matches the path you plan to register. Asset configuration varies by project, so verify the generated build output rather than assuming a source-file path is also the deployed URL.
Register the script through Angular’s provider in the application providers:
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A free scan shows the junk files, broken settings and background clutter dragging Windows down - then fixes them in one click.Free scan · Windows 10 & 11provideServiceWorker('custom-sw.js', options)The first argument is the worker script path; the optional second argument is a SwRegistrationOptions object. Angular documents options for enabling registration, script type, scope, update-via-cache behavior, and registration timing. The stable API documents registerWhenStable:30000 as the default registration strategy; check the API documentation for the Angular version used by your application, since API behavior can evolve. See provideServiceWorker and SwRegistrationOptions.
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Test the production build and deployed scope
Service workers require a secure context: use HTTPS in deployment, with localhost as the development exception. Also account for browsers where service workers are unsupported rather than assuming registration succeeds everywhere. Angular’s overview covers these support and security-context considerations.
- Build the app with its production configuration. Angular’s getting-started guide describes the standard setup with
ng add @angular/pwa, creation ofngsw-config.json, and local testing of a production configuration. - Serve the built app from a suitable context. Confirm that both
custom-sw.jsandngsw-worker.jsresolve at the expected deployed paths. - Test in a private or incognito window. Angular recommends this to reduce interference from an older worker or cached state.
- Verify the behavior you added. Exercise the relevant event, confirm asynchronous work completes, and check that errors are handled. Test both development and production as appropriate for the app.
- Check the worker’s scope and supported browsers. A wrong path or scope can prevent the expected pages from being controlled by the worker.
Check cache configuration before debugging custom code
If a request is cached unexpectedly or not cached at all, the cause may be ngsw-config.json rather than the custom event handler. Angular evaluates asset groups in order, and the first matching data group handles a request. Put more specific data groups before broader ones. Its configuration guide also notes that glob patterns may partially match URLs and that special regular-expression characters may need escaping. See Service Worker configuration file.
Understand updates and recovery
Angular’s deployment guidance says hashed resources are checked for integrity. A browser installs an updated service worker when the worker script is byte-different; changing only response headers does not trigger reinstallation. If a header-only change must trigger installation, Angular documents using a versioned script URL. See Service worker devops.
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For a problematic registration or cache, Angular also documents recovery approaches that rename or remove ngsw.json and use the package’s safety-worker.js to remove unwanted service-worker registrations and caches. These are operational measures, not routine update steps: validate their effects against the application’s deployment setup before using them.
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