App Cache
App Cache (Application Cache) is a deprecated web technology that allows web applications to work offline by caching resources like HTML, CSS, JavaScript, and images in the browser. It uses a manifest file to specify which files should be cached, enabling users to access the application without an internet connection. However, it has been replaced by modern service workers due to significant limitations and bugs.
Developers should learn App Cache primarily for maintaining legacy web applications that still rely on it, as it was widely used in the early 2010s for offline functionality. It's also useful for understanding the evolution of web technologies, but new projects should avoid it in favor of service workers, which offer better control, reliability, and features like background sync and push notifications.