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Angular project error on local debug: Uncaught DOMException: Failed to execute 'importScripts' on 'WorkerGlobalScope

We keep getting an error when developing locally:


service-worker.web.js:33UncaughtDOMException: Failed to execute 'importScripts' on 'WorkerGlobalScope': The script at 'http://localhost:4200/ngsw-worker.js' failed to load.
at http://localhost:4200/service-worker.web.js:33:1 (anonymous) @ service-worker.web.js:33 A bad HTTP response code (404) was received when fetching the script. main.ts:11 Service worker registration failed with: TypeError: Failed to register a ServiceWorker for scope ('http://localhost:4200/') with script ('http://localhost:4200/service-worker.web.js'): ServiceWorker script evaluation failed

When AOT is released, it works perfectly, but it can be annoying to see the exception when developing. I have tried to delete the line "importScripts('./ngsw-worker.js');" from the local mode, but then the automatic reload when saving is disabled

any suggestions?


1 Reply 1 reply marked as answer

TJ Theveshwar Jayakumar Syncfusion Team March 6, 2023 04:58 AM UTC

Hi Ashna,

Greetings from Syncfusion support,


We have evaluated your reported scenario at our end and after further investigation, we found that the issue you are facing is not because of Syncfusion controls. But we would like to inform you that this error message indicates that the service worker script is unable to load the ngsw-worker.js script. Here are some steps you can take to resolve this issue.


  1. Check the file path of ngsw-worker.js and ensure that it is correct. Make sure that the file exists at the specified path.


  1. Check if there are any network issues preventing the file from loading. Try accessing ngsw-worker.js directly from the browser to see if it can be loaded successfully. If not, there might be a server configuration issue or permission issue on the file.


  1. Check if there are any caching issues related to ngsw-worker.js. Try clearing the cache and refreshing the page to see if that resolves the issue.


  1. Make sure that your server is configured to serve the ngsw-worker.js file with the correct MIME type. It should be served as a JavaScript file with the MIME type application/javascript.


  1. Try updating your Angular version or the Angular Service Worker package to the latest version, as this issue may have been resolved in a newer version.



We hope the above provided solution could resolve your reported issue. Please get back to us if you have any concerns.




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