Overview
A page is built from multiple request-response exchanges. Methods, URLs, status codes and headers reveal issues that a simple visual check can miss.
What each message contains
Requests include a method, target, headers and sometimes a body. Responses carry status, headers and content. GET commonly reads data and POST commonly submits it; do not automatically retry operations with side effects.
Status codes provide clues
2xx indicates success, 3xx commonly covers redirects or cache validation, 4xx concerns the request, and 5xx indicates server-side failure. Also determine whether the response came from the edge or the origin.
Read caching headers together
Cache-Control expresses caching policy, while ETag and Last-Modified can support validation. Vary identifies request headers that affect response selection; ignoring those differences can cause incorrect reuse.
- Do not treat private or no-store as permission for shared caching
- Check validation responses and the content version being reused
- Verify how configured rules handle query parameters and cookies
HTTPS protects the transport
HTTPS uses TLS to protect HTTP in transit. Certificates, names and connection settings must align. HTTPS between the browser and edge does not automatically establish encryption between the edge and origin.