networkfirst

NetworkFirst is a web caching strategy used primarily in service workers for Progressive Web Apps and other client-side caching layers. It prioritizes obtaining resources from the network to ensure freshness, with a fallback to cached responses if the network request fails.

How it works: When a resource is requested, the service worker attempts a network fetch first. If the network response is successful, the response is returned to the page and typically cached for future requests. If the network fetch fails due to the user being offline or a network error, the service worker serves the item from the cache if a cached version exists. If neither network nor cache provides a result, a fallback may be returned or the request may fail as appropriate.

When to use: NetworkFirst is suitable for content that benefits from up-to-date data but can tolerate occasional delays while online, such as API responses, non-critical dynamic pages, or user-specific content that changes frequently. It is less appropriate for resources that must work offline or where very fast initial loads are essential.

Advantages and limitations: The strategy tends to deliver fresh content when connectivity is available, while still providing offline access via the cache. However, it can incur higher latency on slow or unstable networks and may waste bandwidth by frequently updating cached copies. Proper error handling and fallback strategies are important to maintain a smooth user experience.

Implementation notes: In practice, developers implement NetworkFirst by attempting a network fetch, then caching successful responses, and falling back to cached data on failure. Libraries such as Workbox provide built-in NetworkFirst strategies to simplify integration.