This browser is no longer supported.
Upgrade to Microsoft Edge to take advantage of the latest features, security updates, and technical support.
![](data:image/svg+xml, %3Csvg xmlns='http://www.w3.org/2000/svg' height='64' class='font-weight-bold' style='font: 600 30.11764705882353px "SegoeUI", Arial' width='64'%3E%3Ccircle fill='hsl(128, 55.00000000000001%, 22%)' cx='32' cy='32' r='32' /%3E%3Ctext x='50%25' y='55%25' dominant-baseline='middle' text-anchor='middle' fill='%23FFF' %3ESR%3C/text%3E%3C/svg%3E)
I have a Blazor WASM app in VS 2022 Community v 17.10.1 that I am trying to run offline, but am getting several "failed to load resource" and one "failed to register a Service Worker" exceptions as shown below.
I followed these instructions to make the app WPA (it wasn't setup that way at first). Consistent with the instructions: the wwwroot files are there, including service-worker.js, manifest.json, and icon-512.png; (2) index.html has the required links and script for the manifest and service worker; and (3) the manifest (.json instead of .webmanifest) looks right.
I'm publishing to Azure with the settings shown below. When I run the published app, the icon that let's me install it appears as it should in the address bar and when I run the installed app it works. But when I disable internet access, the installed app throws the exceptions shown below, including a failure to load manifest.json and blazor.boot.json.
Any idea what I'm missing? I can post images of my wwwroot, index.html and manifest if that might help. Thanks for any thought you have.
![](data:image/svg+xml, %3Csvg xmlns='http://www.w3.org/2000/svg' height='64' class='font-weight-bold' style='font: 600 30.11764705882353px "SegoeUI", Arial' width='64'%3E%3Ccircle fill='hsl(211.20000000000002, 61%, 30%)' cx='32' cy='32' r='32' /%3E%3Ctext x='50%25' y='55%25' dominant-baseline='middle' text-anchor='middle' fill='%23FFF' %3EBS%3C/text%3E%3C/svg%3E)
check that you deployed the service-worker-published.js version. the dev version does no caching.
Thanks for the suggestion, Bruce. I've marked service-worker-published.js (and the other wwwroot files) to Always Copy to Output Directory and am getting the same exceptions. Is that what you mean by deploying this service worker? I must admit to being uncertain about a number of deployment variables as described here.
the deployment process, if specified as release, should have copied service-worker-published.js to service-worker.js in the wwwroot folder copied to the webserver.
to host your app offline, the server worker needs to have cached all required files. if you look service-worker.js is just:
self``.addEventListener('fetch', () => { });
always ignores fetch events.
Thanks again, Bruce. Your simple explanation of the service-worker files helps. But I still can't run offline.
I'm including screenshots of the full list of exceptions, which I should have done initially (I showed only the first ones, incorrectly thinking that later ones cascaded from the first ones, missing that async processing may not have presented them in order). Anyway, the last ones indicate the config file (blazor.boot.json) failed to fetch/load. It's in the Release\net8.0\wwwroot_framework folder where I gather it should be.
I've been reading about the config file here. Clearly key to caching what the app needs to run offline. But this is not suggesting why mine isn't fetching.
If you have the browser dev tools open, be sure disable cache is not set. This bypasses the service worker which performs the cache.
That's not the problem. Disable cache is not set in the installed version of the app.
Doubt this is relevant, but I noticed while checking devtools that there's a deprecated feature being used in onloadwff.js (whatever that is). Devtools says "Unload event listeners are deprecated and will be removed."
I meant the browser dev tools disable cache setting, which disables the service worker that performs the offline cache support.
I am now able to run the app offline. I'm not sure what has enabled that, other than perhaps because I added the tag below in the <head> in index.html. I did this because I wasn't automatically getting updates when I ran the installed version of the app. That is now fixed along with the offline use. Not sure if there are any unintended consequences in this.
<meta content="no-cache, no-store, must-revalidate" />