appcaches

App caches are data caches used by software applications to store copies of data locally, enabling faster access and offline operation. They can reside on device storage or in memory and are managed either by the application itself or by platform-provided APIs. Typical cached items include images, API responses, user preferences, and database query results. Caching decisions are governed by policies such as expiration, eviction, and synchronization, balancing resource use and data freshness.

In the web context, HTML5 Application Cache (appcache) was a historical standard that allowed offline web applications to function by declaring a manifest file listing resources to cache. Browsers would populate a cache with those resources and serve them when the network was unavailable. The system introduced a number of pitfalls: update and validation were not intuitive; applications could receive stale content; manifest changes did not always propagate reliably; and the mechanism had security and reliability concerns across origins. Because of these issues, appcache has been deprecated in favor of programmatic caching via Service Workers and the Cache API.

Today, progressive web apps and modern browsers rely on service workers to intercept network requests and manage a Cache object, giving developers fine-grained control over what to cache, when to update, and how to serve content offline.

Beyond the web, app caches are common in mobile and desktop applications through platform-specific storage areas. Examples include Android's cache directory and iOS caches directory, as well as in-app caching libraries (LRU caches, disk caches) used by apps to reduce network usage and improve responsiveness. Storage limits, eviction policies, and user privacy considerations guide cache design and lifecycle.