HTTP has a concept of conditional requests, where the result, and even the success of a request, can be controlled by comparing the affected resources with a validator. These requests are useful for validating cached content, ensuring that it is only fetched if it differs from the copy that is already available to the browser. Conditional requests are also useful for ensuring the integrity of a document when resuming a download, or preventing lost updates when uploading or modifying a documen...| MDN Web Docs
The HTTP If-None-Match request header makes a request conditional. The server returns the requested resource in GET and HEAD methods with a 200 status, only if it doesn't have an ETag matching the ones in the If-None-Match header. For other methods, the request will be processed only if the eventually existing resource's ETag doesn't match any of the values listed.| MDN Web Docs
Learn about how Astro's islands architecture helps keep sites fast.| Docs
