Definition
DNS is the first step in any page load: before a browser can download anything, it must resolve the domain name to an IP address. A slow DNS adds hundreds of milliseconds to the TTFB. For SEO, performant DNS is essential because it impacts page load time, Googlebot's crawl, and site availability. Best practices include using a premium DNS provider (Cloudflare DNS, Route 53, Google Cloud DNS), implementing DNS prefetching in HTML, reducing the number of third-party domains to resolve, and correctly configuring records (A, CNAME, AAAA for IPv6). DNS record TTL must balance performance (long cache) and flexibility (short cache for migrations).
Key Points
- Slow DNS directly adds milliseconds to TTFB
- Use a premium DNS provider (Cloudflare, Route 53) for fast resolution
- DNS prefetching pre-resolves third-party domains
Practical Examples
DNS migration to Cloudflare
A site migrates its DNS from its basic registrar to Cloudflare and sees DNS resolution time drop from 200ms to 15ms on average, improving overall TTFB.
DNS prefetch
An e-commerce site adds dns-prefetch tags for third-party domains (analytics, image CDN, payment) in the HTML head, saving 100-300ms on initial load.
Frequently Asked Questions
Yes. DNS is the first step in page loading. Slow DNS can add 100-500ms to TTFB, impacting Core Web Vitals and user experience. Googlebot is also affected by DNS performance during crawling.
Cloudflare DNS (1.1.1.1) is the fastest and free. Google Cloud DNS and AWS Route 53 are excellent alternatives. The key is choosing a provider with a global anycast network for fast resolution everywhere.
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Last updated: 2026-02-07