PERFORMANCE · SEO GLOSSARY
Server Response Time (TTFB)
Time to First Byte (TTFB) — the time from a browser (or crawler) making an HTTP request to receiving the first byte of the response from the server. Google\'s threshold for Good TTFB is under 800ms; over 1800ms is Poor. High TTFB directly delays LCP and every other page load metric.
Definition
Server response time, measured as Time to First Byte (TTFB), is the duration from when a browser sends an HTTP GET request to a URL until it receives the first byte of the response. TTFB includes: DNS resolution time, TCP connection time, TLS handshake time (for HTTPS), and actual server processing time (database queries, application server rendering, caching layer). TTFB is the first bottleneck in the page load chain — every subsequent metric (LCP, FCP, total load time) can only start after TTFB completes. Google\'s CrUX thresholds for TTFB: **Good**: under 800ms. **Needs Improvement**: 800ms–1800ms. **Poor**: over 1800ms. Common causes of high TTFB: **No caching** — every request triggers a full database query + server-side render. WordPress with no page caching plugin making uncached PHP+MySQL requests is a typical case. **Distant server** — a European user hitting a US-only server adds 100–200ms of round-trip latency before any server processing begins. Solution: CDN edge caching or a server geographically closer to the primary user base. **Database query latency** — slow or unindexed database queries that delay response generation. **Third-party blocking** — A/B testing scripts or authentication checks that block the response before the first byte. **Hosting tier** — shared hosting with resource contention. Fixes: implement full-page caching (Redis object cache + HTML caching for WordPress via WP Rocket; `Cache-Control: s-maxage` for Next.js static pages via Vercel edge), use a CDN with edge caching close to users, optimise database queries, and use a VPS/dedicated server rather than shared hosting for pages with significant traffic.
Why it matters for SEO
TTFB is the single upstream dependency for all other page performance metrics. An LCP target of 2500ms is nearly impossible if TTFB is 2000ms — there\'s only 500ms left for resource download and render. Google\'s page experience ranking signal uses CrUX field data including Core Web Vitals (LCP, INP, CLS), and a high TTFB that causes LCP failures is a direct ranking factor. High TTFB also slows Googlebot crawls — a slow server means fewer pages crawled per crawl budget.
How DeepSEOAnalysis checks this
The audit measures TTFB directly during the crawl by recording the time from request dispatch to first-byte receipt for every crawled URL. TTFB values are reported per page and as a site-wide average. Pages with TTFB above Google\'s Good threshold (800ms) are flagged. CrUX field data for TTFB (where available in the CrUX dataset) is also included alongside the synthetic crawl measurement.
Useful tools and resources
GLOSSARY
Related terms
performance
Core Web Vitals
Three Google metrics — LCP, INP, and CLS — that measure real-user loading, interactivity, and visual stability.
Read definition →core web vitals
Largest Contentful Paint (LCP)
The Core Web Vital measuring how long it takes for the largest visible content element in the viewport to render — good LCP is under 2.5 seconds at the p75 threshold using real Chrome user data (CrUX).
Read definition →performance
Page Speed
The time it takes for a page to load and become usable — measured by multiple metrics including TTFB, FCP, and Core Web Vitals.
Read definition →technical
Crawl Budget
The number of pages Googlebot will crawl on a site within a given timeframe — determined by crawl rate limit and crawl demand.
Read definition →See how your site scores on Server Response Time (TTFB).
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