An APPCACHE file is a file used by web browsers to enable accessibility of web applications when there is no network connection. It contains copies of resources that make up web applications, such as image (.PNG, .GIF, etc.), .CSS, and .JS files, and are identified by URLs.

APPCACHE files are created to allow web applications to run without an Internet connection, reduce the server load, and hasten webpage load time. The APPCACHE file consists of four optional sections: CACHE - Lists all resources that need to be downloaded and locally stored. NETWORK - Lists all URLs that are loaded via Internet and won't be cached. FALLBACK - Lists replacements for network URLs that are used if the web browser is offline. SETTINGS - Determines settings for application cache behavior.