Created attachment 357722 [details] Compressed site for testing bug When visiting a page that has a cache manifest specified, Safari will fire a checking event. Afterwards, no further events are fired. You would expect a noupdate event to fire afterwards normally. It looks like Safari never actually makes a request to get the cache manifest when this occurs. I checked my server logs and didn't see any requests for the cache manifest file. The easiest way to reproduce the issue is as follows: 1. Setup a server to host the attached html and cache manifest 2. In preferences, set "Safari opens with" to "All windows from last session" 3. Visit the page 4. Close safari 5. Restart your mac 6. Open safari. It should open up your page, but will only fire a checking event. Note that if you then reload the page it will fire a checking event, followed by a noupdate. I have reproduced this on an iPad Air 2 running iOS 12.1.1 and a Macbook Pro running running macOS 10.14 w/ Safari version 12.0 (14606.136.1.9). I can also intermittently reproduce the issue if I just normally visit a page that has a cache manifest specified, but the most consistent way is by restarting the mac. It happens every time if I restart.