This will also work when the site's servers are down. It serves offline content from the local cache if the original fetch fails - it can fail either due to you

This will also work when the site's servers are down. It serves offline content from the local cache if the original fetch fails - it can fail either due to your device's connection, the server, or anything in between. However, since offline content is served after trying the network, it's still going to be slow in flakey network conditions as you wait for the original request to either succeed or give up.