Response Time Test: DNS, TCP, TLS, TTFB Breakdown

DNS: time to resolve domain to IP. TCP: time to establish the TCP connection. TLS: time for the TLS/SSL handshake. TTFB (Time to First Byte): time from request sent to first response byte received. Download: time to transfer the response body.

Under 200ms is excellent, 200–500ms is acceptable, 500ms–1s needs investigation, and over 1s indicates significant backend or network issues. Google Core Web Vitals considers TTFB as a diagnostic metric for LCP (Largest Contentful Paint).

Slow DNS can be caused by: authoritative nameserver latency, complex DNS chains (CNAME → CNAME → A), geographic distance to the resolver, or the domain not being cached. Using a CDN or low-TTL records can make this worse if your nameserver is slow.

Use a CDN (reduces TCP/TLS time via edge proximity), enable HTTP/2 or HTTP/3 (multiplexing reduces overhead), optimize backend processing (reduces TTFB), enable compression (reduces download time), and use persistent connections (eliminates TCP/TLS for subsequent requests).