HTTP cache should cache regardless of status code when freshness information is available

• Component: Page Loading
• Status: NEW ---

[Mark Nottingham]

In HTTP, the status code doesn't have much impact on caching. Specifically, if a response has an explicit freshness lifetime and there aren't any other conditions preventing caching (e.g., method, other cache directives in the request or response), the status code doesn't matter.

Spec:
  http://httpwg.org/specs/rfc7234.html#caching.overview

Allowing new status codes to be cached is important; it allows new extensions to be deployed without updating existing cache implementations.

In testing, Safari TP appears to cache some status codes, but does not cache unknown status codes (e.g., 299, 499, 599), nor does it cache 5xx-series status codes (e.g., 500, 502, 503, 504).

Chrome caches all of these status codes when they have explicit freshness information.

Tests:
  http://w3c-test.org/fetch/http-cache/status.html