HTTP headers / response header
Expires
Expires: Thu, 12 Jun 2026 08:00:00 GMT
What it does
Legacy absolute-time cache expiry. Cache-Control: max-age wins whenever both are present.
The gotcha
Clock skew makes absolute dates fragile — treat Expires as the fallback for ancient caches, not the policy.
Debugging headers on a phone
The fastest way to see what Expires is actually doing is to send the request and read both sides raw — ReqPad shows auto-generated and custom headers for every request, on all six protocols, with history. Related references: status codes · WWW-Authenticate · Content-Encoding · Transfer-Encoding · ETag · Last-Modified · Location
Inspect Expires on a live request.
Build the request, send it, read raw headers and timing — from your iPhone. Free to start.