Your browser just timed everything.
Every DNS lookup, TCP handshake, and byte downloaded to render this page was measured. Here is what the browser recorded.
This Page
Key Resources
Loading resource data...
What Changed on Repeat
Refresh this page to compare cold vs warm cache timing.
What the browser cannot see
The browser measures its own timing precisely, from the moment it starts a DNS lookup to the last byte arriving. But it has no visibility into what happens on the server side. It cannot see how long your request sat in a reverse proxy queue, whether a CDN served a cached copy or fetched from origin, or how many internal hops your request took before a response was generated. The gap between "connection established" and "first byte received" is the closest hint, but even that is a black box.