Infrastructure Speed Test
A full request-lifecycle breakdown for any URL — DNS, TCP, TLS, TTFB and content download — using the browser's Resource Timing API.
🧭 The phases
- DNS — name resolution
- Connect — TCP handshake
- TLS — HTTPS negotiation
- TTFB — server thinking time
- Download — transferring the response
🚀 HTTP/2 & HTTP/3
HTTP/2 multiplexes requests over one connection; HTTP/3 runs over QUIC/UDP and removes head-of-line blocking. If you see http/1.1, upgrading is a quick win.
⚠️ Cross-origin limits
For third-party URLs, browsers hide detailed phase timings unless the server sends Timing-Allow-Origin. You'll still get total time; the breakdown is fullest on your own origin.
Frequently Asked Questions
What does TTFB include?
Time To First Byte covers everything from the moment the request is sent until the first byte of the response arrives — server processing, database queries and queueing. High TTFB usually points at slow backend code or an under-powered server.
Why is the protocol blank for other sites?
Detailed Resource Timing fields (including protocol) are hidden cross-origin unless the server sends a Timing-Allow-Origin header. Test your own origin for the complete breakdown.