PERFORMANCE · SEO GLOSSARY
Time to First Byte (TTFB)
The time between a browser sending an HTTP request and receiving the first byte of the server's response — a measure of server response speed that influences crawl rate and LCP.
Definition
Time to First Byte (TTFB) is the duration from when a browser sends an HTTP request for a URL to when it receives the first byte of the server's response. It includes: DNS lookup time, TCP connection establishment, TLS handshake (for HTTPS), and server processing time (database queries, server-side rendering, cache lookup). TTFB does not include content download time — it measures only the latency before data starts arriving. Web Vitals guidance from Google recommends a TTFB under 800ms as a target for LCP optimisation, since TTFB is the starting point for LCP measurement. Extremely slow TTFB (>2000ms) can also reduce Googlebot's crawl rate — Google throttles crawling for slow servers to avoid overwhelming them.
Why it matters for SEO
TTFB is the first bottleneck in page load time. Even the fastest client-side rendering can't compensate for a 3-second server response time — the browser is idle until that first byte arrives. For sites with server-side rendering (Next.js, Laravel, WordPress), TTFB is primarily driven by server processing time (uncached database queries, slow CMS rendering, cold application startup). For CDN-served static pages, TTFB should be <100ms. High TTFB is often the root cause of poor LCP: Google's research shows that pages with TTFB >1.8s rarely achieve Good LCP. Fixes: server-side response caching (Redis, Varnish), database query optimisation, static generation for pages that don't need dynamic data, CDN edge caching, and reducing server processing time.
How DeepSEOAnalysis checks this
The audit measures TTFB for all crawled pages using HTTP timing headers. Pages with TTFB consistently above 800ms are flagged with specific guidance based on the detected technology stack (WordPress: caching plugin recommendations; Next.js: static vs. server-rendered page identification; generic: CDN and server-side cache suggestions). TTFB results correlate with LCP field data from CrUX — high TTFB and poor LCP often appear together.
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 →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 Frequency
How often Googlebot revisits pages on a site — influenced by crawl budget, update frequency, PageRank, and server response time — determining how quickly new or updated content enters Google's index.
Read definition →performance
INP (Interaction to Next Paint)
The Core Web Vital that measures a page's responsiveness to user interactions — replacing FID in March 2024 as a Google ranking signal. Good INP is under 200ms.
Read definition →See how your site scores on Time to First Byte (TTFB).
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