We Keep Coding

How to clear a service worker cache for index.html page? [duplicate]

I'm playing with the service worker API in my computer so I can grasp how can I benefit from it in my real world apps.
I came across a weird situation where I registered a service worker which intercepts fetch event so it can check its cache for requested content before sending a request to the origin.
The problem is that this code has an error which prevented the function from making the request, so my page is left blank; nothing happens.
As the service worker has been registered, the second time I load the page it intercepts the very first request (the one which loads the HTML). Because I have this bug, that fetch event fails, it never requests the HTML and all I see its a blank page.
In this situation, the only way I know to remove the bad service worker script is through chrome://serviceworker-internals/ console.
If this error gets to a live website, which is the best way to solve it?
Thanks!

I wanted to expand on some of the other answers here, and approach this from the point of view of "what strategies can I use when rolling out a service worker to production to ensure that I can make any needed changes"? Those changes might include fixing any minor bugs that you discover in production, or it might (but hopefully doesn't) include neutralizing the service worker due to an insurmountable bug—a so called "kill switch".
For the purposes of this answer, let's assume you call
navigator.serviceWorker.register('service-worker.js');
on your pages, meaning your service worker JavaScript resource is service-worker.js. (See below if you're not sure the exact service worker URL that was used—perhaps because you added a hash or versioning info to the service worker script.)
The question boils down to how you go about resolving the initial issue in your service-worker.js code. If it's a small bug fix, then you can obviously just make the change and redeploy your service-worker.js to your hosting environment. If there's no obvious bug fix, and you don't want to leave your users running the buggy service worker code while you take the time to work out a solution, it's a good idea to keep a simple, no-op service-worker.js handy, like the following:
// A simple, no-op service worker that takes immediate control.
self.addEventListener('install', () => {
// Skip over the "waiting" lifecycle state, to ensure that our
// new service worker is activated immediately, even if there's
// another tab open controlled by our older service worker code.
self.skipWaiting();
});
/*
self.addEventListener('activate', () => {
// Optional: Get a list of all the current open windows/tabs under
// our service worker's control, and force them to reload.
// This can "unbreak" any open windows/tabs as soon as the new
// service worker activates, rather than users having to manually reload.
self.clients.matchAll({type: 'window'}).then(windowClients => {
windowClients.forEach(windowClient => {
windowClient.navigate(windowClient.url);
});
});
});
*/
That should be all your no-op service-worker.js needs to contain. Because there's no fetch handler registered, all navigation and resource requests from controlled pages will end up going directly against the network, effectively giving you the same behavior you'd get without if there were no service worker at all.
Additional steps
It's possible to go further, and forcibly delete everything stored using the Cache Storage API, or to explicitly unregister the service worker entirely. For most common cases, that's probably going to be overkill, and following the above recommendations should be sufficient to get you in a state where your current users get the expected behavior, and you're ready to redeploy updates once you've fixed your bugs. There is some degree of overhead involved with starting up even a no-op service worker, so you can go the route of unregistering the service worker if you have no plans to redeploy meaningful service worker code.
If you're already in a situation in which you're serving service-worker.js with HTTP caching directives giving it a lifetime that's longer than your users can wait for, keep in mind that a Shift + Reload on desktop browsers will force the page to reload outside of service worker control. Not every user will know how to do this, and it's not possible on mobile devices, though. So don't rely on Shift + Reload as a viable rollback plan.
What if you don't know the service worker URL?
The information above assumes that you know what the service worker URL is—service-worker.js, sw.js, or something else that's effectively constant. But what if you included some sort of versioning or hash information in your service worker script, like service-worker.abcd1234.js?
First of all, try to avoid this in the future—it's against best practices. But if you've already deployed a number of versioned service worker URLs already and you need to disable things for all users, regardless of which URL they might have registered, there is a way out.
Every time a browser makes a request for a service worker script, regardless of whether it's an initial registration or an update check, it will set an HTTP request header called Service-Worker:.
Assuming you have full control over your backend HTTP server, you can check incoming requests for the presence of this Service-Worker: header, and always respond with your no-op service worker script response, regardless of what the request URL is.
The specifics of configuring your web server to do this will vary from server to server.
The Clear-Site-Data: response header
A final note: some browsers will automatically clear out specific data and potentially unregister service workers when a special HTTP response header is returned as part of any response: Clear-Site-Data:.
Setting this header can be helpful when trying to recover from a bad service worker deployment, and kill-switch scenarios are included in the feature's specification as an example use case.
It's important to check the browser support story for Clear-Site-Data: before your rely solely on it as a kill-switch. As of July 2019, it's not supported in 100% of the browsers that support service workers, so at the moment, it's safest to use Clear-Site-Data: along with the techniques mentioned above if you're concerned about recovering from a faulty service worker in all browsers.

You can 'unregister' the service worker using javascript.
Here is an example:
if ('serviceWorker' in navigator) {
navigator.serviceWorker.getRegistrations().then(function (registrations) {
//returns installed service workers
if (registrations.length) {
for(let registration of registrations) {
registration.unregister();
}
}
});
}

That's a really nasty situation, that hopefully won't happen to you in production.
In that case, if you don't want to go through the developer tools of the different browsers, chrome://serviceworker-internals/ for blink based browsers, or about:serviceworkers (about:debugging#workers in the future) in Firefox, there are two things that come to my mind:
Use the serviceworker update mechanism. Your user agent will check if there is any change on the worker registered, will fetch it and will go through the activate phase again. So potentially you can change the serviceworker script, fix (purge caches, etc) any weird situation and continue working. The only downside is you will need to wait until the browser updates the worker that could be 1 day.
Add some kind of kill switch to your worker. Having a special url where you can point users to visit that can restore the status of your caches, etc.
I'm not sure if clearing your browser data will remove the worker, so that could be another option.

I haven't tested this, but there is an unregister() and an update() method on the ServiceWorkerRegistration object. you can get this from the navigator.serviceWorker.
navigator.serviceWorker.getRegistration('/').then(function(registration) {
registration.update();
});
update should then immediately check if there is a new serviceworker and if so install it. This bypasses the 24 hour waiting period and will download the serviceworker.js every time this javascript is encountered.

For live situations you need to alter the service worker at byte-level (put a comment on the first line, for instance) and it will be updated in the next 24 hours. You can emulate this with the chrome://serviceworker-internals/ in Chrome by clicking on Update button.
This should work even for situations when the service worker itself got cached as the step 9 of the update algorithm set a flag to bypass the service worker.

We had moved a site from godaddy.com to a regular WordPress install. Client (not us) had a serviceworker file (sw.js) cached into all their browsers which completely messed things up. Our site, a normal WordPress site, has no service workers.
It's like a virus, in that it's on every page, it does not come from our server and there is no way to get rid of it easily.
We made a new empty file called sw.js on the root of the server, then added the following to every page on the site.
<script>
if (navigator && navigator.serviceWorker && navigator.serviceWorker.getRegistration) {
navigator.serviceWorker.getRegistration('/').then(function(registration) {
if (registration) {
registration.update();
registration.unregister();
}
});
}
</script>

In case it helps someone else, I was trying to kill off service workers that were running in browsers that had hit a production site that used to register them.
I solved it by publishing a service-worker.js that contained just this:
self.globalThis.registration.unregister();

Service Worker fetch event not triggered for service worker itself

I noticed that the fetch event of a service worker is no longer triggered when the service worker script itself is loaded in the browser. For example, when we have a new version of a service worker, the old service workers fetch event is not triggered. As consequence, the old service worker can no longer check the content of the new service worker.
I'm sure this was possible before and I would like to know if this is a bug or if any changes were made regarding to that. I did not find anything in the official repository or W3C draft regarding to this change.
To verify that the fetch event is not triggered I programmed a small example service worker with a version number (see code). I have tested it the following way:
Install first version of service worker
Increase the version number to two.
Reload the page -> So that the new sw.js file is installed in the browser.
Check the chrome logs -> ChromeLogs
Example 'sw.js':
const version = 1;
console.log(`SW with v${version} executed`);
async function onFetch(event) {
// Not triggered for sw.js
console.log(`fetching: ${event.request.url} with v${version}`);
return await fetch(event.request);
}
async function onInstall() {
console.log(`sw v${version} install`);
await self.skipWaiting();
}
async function onActivate() {
console.log(`sw v${version} activate`);
await self.clients.claim();
}
self.addEventListener('fetch', event => event.respondWith(onFetch(event)));
self.addEventListener('install', event => event.waitUntil(onInstall()));
self.addEventListener('activate', event => event.waitUntil(onActivate()));
As we can see from the logs, the sw.js file was not fetched, but another fiel (test.js) was fetched before the new service worker was installed. I included the test.js javascript file to see if the service worker was fetching anything. So from this test we can see that the fetch event is not triggered for service worker script itself.
What I would like to know is, is there any way to fetch the new service worker javascript file before it gets loaded within the old service worker? Are there any other events that make this possible? I do not need to intercept the script from executing or replacing the old service worker. I just want to check the content of the new service worker before it is loaded.
EDIT:
<html>
<body>
<h1>hello</h1>
<script src="test.js"></script>
<button onclick="runFetch()">fetch</button>
<h2 id="swVersion"></h2>
<script>
navigator.serviceWorker.register('/sw.js'); // First Installation
fetch('/sw.js'); // Triggers fetch event, but is independent from update routine.
async function runFetch() {
console.log(await fetch('/sw.js'));
}
</script>
</body>
</html>

The service worker update check that is initiated by the browser always bypasses all service worker fetch handlers. It might end up being fulfilled by the HTTP Cache, although all modern browsers default to also bypassing the HTTP Cache and going straight to the network.
I'm fairly confident that no browser has ever triggered the previous service worker's fetch event handler when performing the service worker update check, as that's explicitly forbidden by the service worker specification (the service-workers mode of the update request is required to be set to 'none'). This helps developers avoid scenarios in which an old service worker could get "stuck" if it did something incorrect when processing the fetch event for a new service worker.
I'm not sure why you might have thought otherwise—perhaps you are thinking about the HTTP Cache interaction. Or perhaps you're thinking about a scenario in which a web app explicitly calls fetch('service-worker.js') to check to see if a service worker exists at a given URL, which will trigger the fetch handler of the service worker in control of a given page. But calling fetch('service-worker.js') is very different from the service worker update check.

Is it reliable to unregister service worker on window.unload event?

I am using something like this to unregister my service worker:
window.addEventListener("unload", () =>{
registration.unregister().then(function(successs) {
if(successs){
console.log("Unregister succesfull!");
}
else {
console.log("unregister unsuccessfull!!");
}
});
});
Since the unregister function returns a promise, it seems that the unregister process is asnyc. So is it reliable to do this unregistration on the unload event?
I have tested on Chrome and it works, but can't find anything in the spec or anywhere that can validate whether what I am doing will always work.
MORE INFO
I know that it seems weird unregistering the service worker on document unload. But I am not using the service worker for caching or notification or other PWA stuff. I am using to serve a dummy HTML page that I generate at runtime. So I just open an iframe with some dummy src and start intercepting all the requests from that iframe from the service worker. I want this service worker to be unregistered after the user closes the tab.

There is a working example that can be found via this Look at the RegisterServiceWorker.js file that is called from TravelManager.html.
I don't get any console output after the call so assume the promise is not resolved? Either way what does it do? IMHO the registration of a Service Worker (intrinsically for many clients/pages) should not be bound to one page.
The manifest registration/declaration functionality seems to be there?
What do you want the unregister to do?

I wouldn't tie it to an event on one page, otherwise having multiple tabs open of the same page will be hard to handle. Personally I'd have the service worker query for clients with setInterval and if the number of clients drops to zero, unregister itself (with self.registration.unregister()).
Edit: it turns out the above doesn't work due to web workers getting eventually killed. I've ended up using the above strategy but instead of setInterval, every time the site is closed it sends a message to the service worker which then checks how many clients it still has.

How to update service worker cache in PWA?

I use service worker with sw-toolbox library. My PWA caches everything except API queries (images, css, js, html). But what if some files will be changed someday. Or what if service-worker.js will be changed.
How application should know about changes in files?
My service-worker.js:
'use strict';
importScripts('./build/sw-toolbox.js');
self.toolbox.options.cache = {
name: 'ionic-cache'
};
// pre-cache our key assets
self.toolbox.precache(
[
'./build/main.js',
'./build/main.css',
'./build/polyfills.js',
'index.html',
'manifest.json'
]
);
// dynamically cache any other local assets
self.toolbox.router.any('/*', self.toolbox.cacheFirst);
// for any other requests go to the network, cache,
// and then only use that cached resource if your user goes offline
self.toolbox.router.default = self.toolbox.networkFirst;
I don't know what is the usual method to update cache in PWA. Maybe PWA should send AJAX request in background and check UI version?

AFAIK the sw_toolbox does not have a strategy for cache with network update. This is really what you want I think.
You want to modify the cache-network race strategy - > https://jakearchibald.com/2014/offline-cookbook/#cache-network-race
Instead of just letting the loser fade away, once the network responds you will want to update the client. This is a little more advanced that I have time or time to explain here.
I would post a message to the client to let it know there is an update. You may want to alert the user to the update or just force the update.
I don't consider this to be an edge case, but a very common, but advanced scenario. I hope to publish a more detailed solution soon.

There is nice solution written here where he states (in a nutshell) to either not use cache-first strategy or update a UX pattern of displaying a "Reload for the latest updates."

I dealt with services workers without using any library and the solution I ended up coming up with involved a bit of server side code and some client side. The strategy in a nutshell
Firstly the variables you will need and where:
On the server side have a "service worker version" variable (Put this in a database or config file if you are using something like php that will update immediately on the server side without requiring a redeploy. Let's call it serverSWVersion
On one of the javascript files you cache (I have a javascript file dedicated to this) have a global variable that will also be the "service worker version". Let's call it clientSWVersion
Now how to use the two:
Whenever a person lands on the page make an ajax call to your server to get the serverSWVersion value. Compare this with the clientSWVersion value.
If the values are different that means your web app version is not
the latest.
If this is the case then unregister the service worker and refresh the page so that the service worker will be re registered and the new files will be cached.
What to actually do when new file is available
Update the serviceSWVersion and clientSWVersion variables and upload to server where applicable.
When a person visits again then the service worker should be re registered and all the cached files will be retrieved.
I have provided a php server side based code that I used while I was implementing this strategy. It should show you the principles. Just drop the "Exercise" folder in a htdocs of a php server and it should work without you having to do anything else. I hope you find it useful... And remember you could just use a database instead of a config file to store the server side service worker variable if you are using some other server instead of php:
Zip file with code:
ServiceWorkerExercise.zip

When a service worker is altered, the browser will install it, but the new version will not be activated until the browser tab or PWA app window is closed and re-opened.
So, if you change the cache name, the new cache will not serve any files until the browser re-opens, nor will the old cache be deleted until that time.
You can detect service worker changes in your page javascript using registration.onupdatefound and ask the user to close and re-open the window - something like this:
// register the service worker
navigator.serviceWorker.register('sw.js').then(function(registration)
{
registration.onupdatefound = function()
{
console.log("ServiceWorker update found.");
alert("A new version is available - please close this browser tab or app window and re-open to update ... ");
}
}, function(err)
{
console.log('ServiceWorker registration failed: ', err);
});

change self.toolbox.router.any('/', self.toolbox.cacheFirst); to self.toolbox.router.any('/', self.toolbox.fastest);

How can I remove a buggy service worker, or implement a "kill switch"?

I'm playing with the service worker API in my computer so I can grasp how can I benefit from it in my real world apps.
I came across a weird situation where I registered a service worker which intercepts fetch event so it can check its cache for requested content before sending a request to the origin.
The problem is that this code has an error which prevented the function from making the request, so my page is left blank; nothing happens.
As the service worker has been registered, the second time I load the page it intercepts the very first request (the one which loads the HTML). Because I have this bug, that fetch event fails, it never requests the HTML and all I see its a blank page.
In this situation, the only way I know to remove the bad service worker script is through chrome://serviceworker-internals/ console.
If this error gets to a live website, which is the best way to solve it?
Thanks!

I wanted to expand on some of the other answers here, and approach this from the point of view of "what strategies can I use when rolling out a service worker to production to ensure that I can make any needed changes"? Those changes might include fixing any minor bugs that you discover in production, or it might (but hopefully doesn't) include neutralizing the service worker due to an insurmountable bug—a so called "kill switch".
For the purposes of this answer, let's assume you call
navigator.serviceWorker.register('service-worker.js');
on your pages, meaning your service worker JavaScript resource is service-worker.js. (See below if you're not sure the exact service worker URL that was used—perhaps because you added a hash or versioning info to the service worker script.)
The question boils down to how you go about resolving the initial issue in your service-worker.js code. If it's a small bug fix, then you can obviously just make the change and redeploy your service-worker.js to your hosting environment. If there's no obvious bug fix, and you don't want to leave your users running the buggy service worker code while you take the time to work out a solution, it's a good idea to keep a simple, no-op service-worker.js handy, like the following:
// A simple, no-op service worker that takes immediate control.
self.addEventListener('install', () => {
// Skip over the "waiting" lifecycle state, to ensure that our
// new service worker is activated immediately, even if there's
// another tab open controlled by our older service worker code.
self.skipWaiting();
});
/*
self.addEventListener('activate', () => {
// Optional: Get a list of all the current open windows/tabs under
// our service worker's control, and force them to reload.
// This can "unbreak" any open windows/tabs as soon as the new
// service worker activates, rather than users having to manually reload.
self.clients.matchAll({type: 'window'}).then(windowClients => {
windowClients.forEach(windowClient => {
windowClient.navigate(windowClient.url);
});
});
});
*/
That should be all your no-op service-worker.js needs to contain. Because there's no fetch handler registered, all navigation and resource requests from controlled pages will end up going directly against the network, effectively giving you the same behavior you'd get without if there were no service worker at all.
Additional steps
It's possible to go further, and forcibly delete everything stored using the Cache Storage API, or to explicitly unregister the service worker entirely. For most common cases, that's probably going to be overkill, and following the above recommendations should be sufficient to get you in a state where your current users get the expected behavior, and you're ready to redeploy updates once you've fixed your bugs. There is some degree of overhead involved with starting up even a no-op service worker, so you can go the route of unregistering the service worker if you have no plans to redeploy meaningful service worker code.
If you're already in a situation in which you're serving service-worker.js with HTTP caching directives giving it a lifetime that's longer than your users can wait for, keep in mind that a Shift + Reload on desktop browsers will force the page to reload outside of service worker control. Not every user will know how to do this, and it's not possible on mobile devices, though. So don't rely on Shift + Reload as a viable rollback plan.
What if you don't know the service worker URL?
The information above assumes that you know what the service worker URL is—service-worker.js, sw.js, or something else that's effectively constant. But what if you included some sort of versioning or hash information in your service worker script, like service-worker.abcd1234.js?
First of all, try to avoid this in the future—it's against best practices. But if you've already deployed a number of versioned service worker URLs already and you need to disable things for all users, regardless of which URL they might have registered, there is a way out.
Every time a browser makes a request for a service worker script, regardless of whether it's an initial registration or an update check, it will set an HTTP request header called Service-Worker:.
Assuming you have full control over your backend HTTP server, you can check incoming requests for the presence of this Service-Worker: header, and always respond with your no-op service worker script response, regardless of what the request URL is.
The specifics of configuring your web server to do this will vary from server to server.
The Clear-Site-Data: response header
A final note: some browsers will automatically clear out specific data and potentially unregister service workers when a special HTTP response header is returned as part of any response: Clear-Site-Data:.
Setting this header can be helpful when trying to recover from a bad service worker deployment, and kill-switch scenarios are included in the feature's specification as an example use case.
It's important to check the browser support story for Clear-Site-Data: before your rely solely on it as a kill-switch. As of July 2019, it's not supported in 100% of the browsers that support service workers, so at the moment, it's safest to use Clear-Site-Data: along with the techniques mentioned above if you're concerned about recovering from a faulty service worker in all browsers.

You can 'unregister' the service worker using javascript.
Here is an example:
if ('serviceWorker' in navigator) {
navigator.serviceWorker.getRegistrations().then(function (registrations) {
//returns installed service workers
if (registrations.length) {
for(let registration of registrations) {
registration.unregister();
}
}
});
}

That's a really nasty situation, that hopefully won't happen to you in production.
In that case, if you don't want to go through the developer tools of the different browsers, chrome://serviceworker-internals/ for blink based browsers, or about:serviceworkers (about:debugging#workers in the future) in Firefox, there are two things that come to my mind:
Use the serviceworker update mechanism. Your user agent will check if there is any change on the worker registered, will fetch it and will go through the activate phase again. So potentially you can change the serviceworker script, fix (purge caches, etc) any weird situation and continue working. The only downside is you will need to wait until the browser updates the worker that could be 1 day.
Add some kind of kill switch to your worker. Having a special url where you can point users to visit that can restore the status of your caches, etc.
I'm not sure if clearing your browser data will remove the worker, so that could be another option.

I haven't tested this, but there is an unregister() and an update() method on the ServiceWorkerRegistration object. you can get this from the navigator.serviceWorker.
navigator.serviceWorker.getRegistration('/').then(function(registration) {
registration.update();
});
update should then immediately check if there is a new serviceworker and if so install it. This bypasses the 24 hour waiting period and will download the serviceworker.js every time this javascript is encountered.

For live situations you need to alter the service worker at byte-level (put a comment on the first line, for instance) and it will be updated in the next 24 hours. You can emulate this with the chrome://serviceworker-internals/ in Chrome by clicking on Update button.
This should work even for situations when the service worker itself got cached as the step 9 of the update algorithm set a flag to bypass the service worker.

We had moved a site from godaddy.com to a regular WordPress install. Client (not us) had a serviceworker file (sw.js) cached into all their browsers which completely messed things up. Our site, a normal WordPress site, has no service workers.
It's like a virus, in that it's on every page, it does not come from our server and there is no way to get rid of it easily.
We made a new empty file called sw.js on the root of the server, then added the following to every page on the site.
<script>
if (navigator && navigator.serviceWorker && navigator.serviceWorker.getRegistration) {
navigator.serviceWorker.getRegistration('/').then(function(registration) {
if (registration) {
registration.update();
registration.unregister();
}
});
}
</script>

In case it helps someone else, I was trying to kill off service workers that were running in browsers that had hit a production site that used to register them.
I solved it by publishing a service-worker.js that contained just this:
self.globalThis.registration.unregister();