How to properly invalidate an HTML5 Cache Manifest for online/offline web apps?

user_108159 0
Viewed 39571

I'm currently using a Cache Manifest (as described here). This effectively makes the necessary resources to run the application available when the user is offline.

Unfortunately, it works a little too well.

After the cache manifest is loaded, Firefox 3.5+ caches all of the resources explicitly referenced in the cache manifest. However, if a file on the server is updated and the user tries force-refreshing the page while online (including the cache-manifest itself), Firefox will absolutely refuse to fetch anything. The application remains completely frozen at the last point it was cached. Questions:

  1. I want Firefox to effectively only rely on the cached resources when the network connection fails. I've tried using the FALLBACK block, but to no avail. Is this even possible?
  2. If #1 is not possible, is it possible for the user to force-refresh a page and bypass this cache (ctrl-F5 doesn't do it and neither does clearing the browser's cache, shockingly) short of clearing their private data? Alternatively, does the cache-manifest mechanism support expiry headers and is its behavior with respect to this documented anywhere?
offline-caching firefox caching html
6 Answers

I had the same problem: once Firefox saved the offline files, it would not reload them ever. Chrome worked as expected, it checked the manifest file for changes and reloaded everything if the manifest file changed. Firefox didn't even download the manifest file from the server, so it could not notice changes.

After investigation, I found out that Firefox was caching the cache manifest file (old fashioned cache, not the offline cache). Setting the cache header of the manifest file to Cache-Control: no-cache, private solved the problem.

user_953690
Related