Time to First Byte (TTFB)
Also: TTFB, server response time, first byte time
TTFB is primarily a server side metric, distinct from total page load time (which includes JavaScript execution and image decoding). A site can have fast total load time but slow TTFB if the server takes time to generate the response. WordPress sites with heavy page builders, dynamic queries, and uncached pages frequently exceed 1 second TTFB.
The fix for slow TTFB is structural. Move to a server side rendered framework (Astro, Next.js SSR), deploy on a CDN edge (Vercel, Cloudflare Pages, Netlify), and aggressively cache static content. A static site on Vercel typically delivers TTFB under 200 milliseconds globally. WordPress can reach 400 milliseconds with a fast theme, full page caching, and edge delivery, but rarely does so without deliberate optimization.
Cited facts
- AI crawlers abandon slow responses. KailxLabs target TTFB is under 400 milliseconds for retrieval readiness.
- A 2 second TTFB causes frequent crawler abandonment by GPTBot and PerplexityBot before any HTML transfers.