Bug 49238

Summary: Link prefetch launches subresource requests too aggressively
Product: WebKit Reporter: Gavin Peters <gavinp>
Component: DOMAssignee: Nobody <webkit-unassigned>
Status: UNCONFIRMED ---    
Severity: Normal CC: achristensen, ad, adieulot, ap, beidson, koivisto, webkit-bug-importer
Priority: P2 Keywords: InRadar
Version: 528+ (Nightly build)   
Hardware: All   
OS: All   
URL: http://http://www.belshe.com/test/prefetch2.html
Bug Depends on: 194539    
Bug Blocks:    

Description Gavin Peters 2010-11-08 20:35:40 PST 
Look at the linked URL, and see the resource loading order.  The launch of prefetch requests is occurring too early.  Prefetch requests should not be launched while, for instance, the onload is pending.

http://code.google.com/p/chromium/issues/detail?id=61476
Comment 1 Andy Davies 2020-07-23 12:09:09 PDT 
This issue still applies in iOS 13.5.1 and Safari 13.1 on mojave

It's particularly bad if the HTTP/2 server doesn't support effective prioritisation as Safari makes the requests at a low priority but the server ignores this and responds, potentially blocking higher priority responses. 

See  https://andydavies.me/blog/2020/07/08/rel-equals-prefetch-and-the-importance-of-effective-http-slash-2-prioritisation/
Comment 2 Radar WebKit Bug Importer 2020-07-23 13:36:50 PDT 
<rdar://problem/66009869>