iOS6 Safari Caching POST Responses

With the release of iOS6 mobile Safari started caching POST responses. Mark Nottingham talks through the related RFCs to see how this lines up with the HTTP specs. Worth a read for the details, here is the conclusion:

even without the benefit of this context, they’re still clearly violating the spec; the original permission to cache in 2616 was contingent upon there being explicit freshness information (basically, Expires or Cache-Control: max-age).

So, it’s a bug. Unfortunately, it’s one that will make people trust caches even less, which is bad for the Web. Hopefully, they’ll do a quick fix before developers feel they need to work around this for the next five years.

Over the years I’ve run across a handful of services and applications that claim to be able to cache HTTP POST responses. In every case that turned out to be a bad decision.