Technical SEO

DNS Resolution Time

Quick Definition

DNS resolution time is the milliseconds spent translating a hostname to an IP address before any HTTP connection can begin — a hidden component of TTFB.

In context

DNS resolution is often the silent culprit behind slow first-byte times, especially for visitors on cellular networks or in regions far from the authoritative DNS servers. Mitigation: use a fast managed DNS provider (Cloudflare, Route 53, NS1) with anycast, low TTLs only for active migrations, dns-prefetch for critical third parties, and monitor DNS time in CrUX field data. For Canadian sites serving international traffic, DNS provider geography matters — east-coast-only nameservers slow down requests from BC and Asia.

Example

A Toronto B2B SaaS moved DNS from a regional registrar to Cloudflare anycast and saw global p75 DNS resolution drop from 80ms to under 20ms.

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