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warningSEO RULE · R20

Slow page response (TTFB): diagnose and fix high server response time

Time to First Byte (TTFB) above 600ms means your server is slow before the browser can even start rendering. It hurts Core Web Vitals (LCP especially), hurts rankings, and increases bounce. Most slow TTFBs come from one of three root causes: unoptimised database queries, no caching, or undersized hosting.

Time to First Byte (TTFB) above 600ms means your server is slow before the browser can even start rendering. It hurts Core Web Vitals (LCP especially), hurts rankings, and increases bounce. Most slow TTFBs come from one of three root causes: unoptimised database queries, no caching, or undersized hosting. TTFB is the time between the browser sending an HTTP request and receiving the first byte of the response. It is the cleanest measure of pure server performance, independent of what the page contains.

Last updated·part of the 50-rule library

What it is

TTFB is the time between the browser sending an HTTP request and receiving the first byte of the response. It is the cleanest measure of pure server performance, independent of what the page contains.

Why it matters

TTFB is a direct input to LCP (Largest Contentful Paint), one of the Core Web Vitals Google uses for ranking. A 1.2s TTFB makes a "Good" LCP impossible regardless of how fast the rest of the page is. Beyond ranking: every 100ms of TTFB reduces conversion rate (e-commerce studies consistently show 1–2% per 100ms).

How to fix it

  1. Measure TTFB across multiple regions. Use WebPageTest, GTmetrix, or your monitoring tool from 3+ geographic locations. A site that is fast from your office but slow elsewhere usually needs a CDN.
  2. Put a CDN in front. CloudFront, Cloudflare, Fastly, or Bunny will cache static responses at edge locations close to users. For most sites this collapses TTFB by 60-90%.
  3. Add full-page caching for HTML. If your CMS regenerates the same HTML on every request (WordPress + WooCommerce without a page cache is the classic offender), a page-cache plugin or Varnish in front will fix it.
  4. Profile slow database queries. Slow DB queries are the #1 cause of slow TTFB on dynamic sites. Turn on a query log, find the queries over 200ms, add the missing indexes.
  5. Right-size your hosting. If TTFB spikes correlate with traffic, you are CPU- or memory-starved. Upgrade or move to a serverless/autoscaling host.

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