It uses cache-control headers to know if the cache is outdated (max-age and eTag). If it is outdated the cached version is shown directly and the server is requested for an update. If the server sends a new image it updates the image directly.
It uses cache-control headers to know if the cache is outdated (max-age and eTag). If it is outdated the cached version is shown directly and the server is requested for an update. If the server sends a new image it updates the image directly.