Make sure the ServiceWorker (sw.js) is not being cached by the server (Cache-Control: no-store) and that it has a deterministic name (no hashing).
Make sure your webapp is served with HTTPS (or localhost for development).
Make sure the browser has cached the latest resources, follow the steps outlined in the updates doc.
Automatic updates isn't the default behavior, but can be achieved using the autoUpdate option
offline-plugin automatically caches all resources generated by webpack. Any other resource needs to be explicitly cached as external.
The ServiceWorker can only serve resources within its scope. Serve your sw file from the root of your public folder, or supply the correct ServiceWorker.scope option.
Specify a unique ServiceWorker.cacheName to avoid it being overridden.
webpack-dev-server compatibility is unknown for the moment, so if you are using hot reloading, ServiceWorker might not work as it's supposed to.
Make sure you are using the correct prefetchRequest.credentials to allow for cookies.
offline-plugin is probably not configured to handle these routes. See the appShell option.
There are multiple ways to fix this depending on your setup. One way is to set cacheMaps.requestTypes to ['navigate'], caching only those requests.
AppCache.events are known to be a bit buggy (see updates). Try to avoid using them if possible.
offline-plugin can cache resources served from a CDN, given the correct configuration. Make sure the resources are served with the correct headers.
DOMException: Failed to register a ServiceWorker: The script has an unsupported MIME type ('text/html') Error
Make sure your webserver is serving your assets (including sw.js) with the correct mime type. Also, make sure you are using relative / absolute paths correctly (see the FAQ regarding this). Also make sure that ServiceWorker and/or AppCache files are generated into the correct folder. You may use ServiceWorker.output and AppCache.output to change the output path. See options for details.
Some errors, like being unable to fetch the ServiceWorker file, originates from the browser, network or server and are out of control of offline-plugin. Here is a list of common errors and their causes.
TypeError: Failed to update a ServiceWorker: A bad HTTP response code (500) was received when fetching the script.
This is a server error. Whatever happens there - it shouldn't. Could be that the server is temporarily down (e.g. changing a deployment on Zeit).
TypeError: Failed to fetch
This is the most generic error you will receive. It typically happens when there's no network connection - it simply can't fetch the file.
AbortError: Failed to update a ServiceWorker: The request to fetch the script was interrupted.
This is a network error - something interrupted the connection. It might be due to the network connection being changed or temporarily lost (it happens all the time in the wild).
TypeError: Script URL https://my-page.com/sw.js fetch resulted in error: An SSL error has occurred and a secure connection to the server cannot be made.
This is a proxy issue. Ie. someone sitting at an airport or on a train and that network injects fake HTTPS certificates (man in the middle).
As the above errors are out of the control of offline-plugin, there is nothing we can do to prevent them. What you may do if you receive any of them is to catch them in your code and try to reschedule the update. Also make sure that your server works correctly and remove any potential bugs / error situation causing HTTP 500 Internal Server Error.