Question: So what is the manifest file?
Answer: To be abrupt, it’s the file with the extension .manifest, but this file is basically what allows your web application to be offline. On it is a list of items that it tells your browser to download, or “cache”, and lets you use those files later when you don’t have an active internet connection.
The manifest file can be both helpful and annoying, as one thing you will need to keep in mind is that once your web application successfully recognizes your manifest file and caches it, the only way to update what you are working on (trying to see any new results of modified code since the last “cache download”), is to update the manifest file itself (done through a swapCache command, but you’ll learn about that later). Unless there is a new manifest file that is at least one byte different than the previous, your browser will continue to run off the old manifest file, using files that it had previously cached, rather than the new modified ones you wish to try.
This section will teach you how to add the manifest mime type to your server, how to create the manifest file (and what to put in it), what the different cache statuses mean, and a clever way to check whether or not your manifest file is working.