I've been investigating the Pragma header, since there are already two other cache-busting HTTP response headers (Cache-Control & Expires), and I was interested in which browsers use(d) the old HTTP 1.0 one.
It turns out the spec only defines Pragma behavior (
no-cache) for HTTP 1.0 requests, not responses.
The only specific browser mentions I can find is for IE4, which seems to require 32 KB of content before honoring it as a
<meta> element, meaning that as a header it never worked even when that browser was relevant, and Netscape 4 which apparently also didn't work.
Has anyone observed a reproducible (and desirable) change in behavior by using the Pragma HTTP header in a response, distinct from the functionality of Cache-Control or Expires?