Response time checker

Find out whether a slow page is slow because of DNS, the network path, the TLS handshake or the application itself.

How it measures

One GET request from a single probe location with an 8-second deadline; redirects are followed (up to five) and their time is included in the total.
Phases are timed from socket events: resolve, connect, TLS handshake, first response byte and body download (capped at 128 KiB).
No caching, no keep-alive reuse: every run is a cold connection, which is what a first-time visitor experiences.

A single measurement from one location; latency differs by region and over time. Repeat a few times before drawing conclusions.
This is server response time, not page load time: scripts, images and rendering are not measured. Real user monitoring covers that.
Bodies larger than 128 KiB are not fully downloaded, so the download phase is a lower bound for big pages.

Slow DNS resolve: Long resolve times usually point to slow authoritative name servers or low TTLs forcing frequent lookups. Compare resolvers with the DNS propagation checker.
Slow TLS handshake: Large certificate chains, OCSP stapling problems or servers without TLS 1.3 add round trips. Check the HTTPS configuration checker.
High time to first byte: The server accepted the request but took long to answer: look at application code, database queries and upstream calls.