Which HTML5 feature historically enabled offline caching via a manifest file but is largely superseded by service workers?

Which HTML5 feature historically enabled offline caching via a manifest file but is largely superseded by service workers?

• A. LocalStorage
• B. IndexedDB
• C. Canvas API
• D. AppCache

Answer: (D)

Offline caching via a manifest file is provided by the Application Cache. It let a web page declare a list of resources to cache for offline use by attaching a manifest to the HTML and listing assets in a .appcache file. The browser would then serve those cached resources when the user was offline, allowing the app to run without a network connection. This approach, while once common, has significant limitations: updates to cached resources could be brittle, cache state could become stale, and you had limited, brittle control over when and how resources were updated. Service workers fix these issues by giving developers a programmable cache with fetch interception, dynamic caching, explicit versioning, and more reliable update paths, making offline behavior far more robust. LocalStorage and IndexedDB are for general client-side data storage, not manifest-based offline caching, and the Canvas API is for drawing graphics, not caching resources.

Offline caching via a manifest file is provided by the Application Cache. It let a web page declare a list of resources to cache for offline use by attaching a manifest to the HTML and listing assets in a .appcache file. The browser would then serve those cached resources when the user was offline, allowing the app to run without a network connection. This approach, while once common, has significant limitations: updates to cached resources could be brittle, cache state could become stale, and you had limited, brittle control over when and how resources were updated. Service workers fix these issues by giving developers a programmable cache with fetch interception, dynamic caching, explicit versioning, and more reliable update paths, making offline behavior far more robust. LocalStorage and IndexedDB are for general client-side data storage, not manifest-based offline caching, and the Canvas API is for drawing graphics, not caching resources.