I’ve been using HTML5 Offline caching on my website for a while and for some reasons I am considering turning it off. To my surprise it doesn’t work.
This is how I’ve implemented HTML5 Offline caching.
In my index.html I give path to the manifest file
<html manifest="app.manifest">
In the app.manifest file I list all the js/css/png file that I would like to be cached by the browser for offline usage. Every time I deploy updates, I update the app.manifest file, which causes the browser to fetch latest version of all the files listed in the manifest file.
In order to turn off the offline caching, I changed my index.html’s opening tag to
<html>
I made a dummy change to app.manifest file, so that browser (which has already cached my website), will detect the change and download latest version of all the files (including index.html).
What I noticed is, the browser indeed gets the latest version of all the files. I see the new <html> tag in the updated version without the manifest declaration, however the behavior of the browser for future changes does not change. i.e. I now expect the browser to immediately fetch the new version of the index.html file, when it’s changed on server. However that doesn’t happen. The browser doesn’t download updated index.html until I make any changes to the manifest file.
Thus it appears to me that the browser has permanently associated app.manifest file with my website URL and it won’t get rid of it even when I don’t mention it in <html> tag.
I have tested this on both Google Chrome and Firefox, same results. I also tried restarting Chrome, but it won’t forget that my site ever had app.manifest defined for it. I haven’t found any discussion on this aspect of offline caching on the web.
Update: I managed to get rid of the behavior in Chrome by clearing all the browsing data (by going to settings). But that’s not something I can tell the users to do.
Make the manifest URL return a 404 to indicate you don’t want offline web applications anymore. According to Step 5 of HTML5 §5.6.4, this marks the cache as obsolete, and will remove it.
You can also manually delete the offline web application in Chrome by going to
about:appcache-internals.