TTFB and Core Web Vitals
TTFB is the foundation everything else builds on. Every millisecond of server response time adds directly to your LCP score.
Time to First Byte is the time from when a browser makes a request until the first byte of the server's response is received. It's not a Core Web Vital itself, but it sets the absolute floor for LCP — no page can achieve good LCP if the server takes 2 seconds to respond.
TTFB encompasses four phases: DNS resolution (time to look up the domain's IP), TCP connection (network handshake), TLS negotiation (HTTPS overhead), and server processing (the time your server spends generating the response). The last phase is most controllable — TTFB improvements typically come from faster servers, CDN caching, and optimised database queries.
For Next.js and other SSR frameworks, TTFB improvements come from edge deployment and streaming. Using the Edge Runtime for pages that don't require full Node.js delivers responses from CDN PoPs close to users. Streaming HTML with React Suspense allows the browser to receive and start rendering the page shell before server data queries complete.
FAQ
What is a good TTFB?
Google recommends TTFB under 800ms. For highly-optimised sites using edge caching, TTFB under 200ms is achievable for cached pages. Under 500ms is a practical target for most dynamic server-rendered pages.
How does TTFB affect LCP?
TTFB sets the floor for LCP. If your server takes 1.2s to respond, your LCP cannot be under 1.2s. Every millisecond of TTFB adds directly to LCP — fixing TTFB is often the highest-ROI LCP improvement.
How do I reduce TTFB?
The most effective approaches are: use a CDN with edge caching for static and semi-static pages, deploy to a region close to your users, optimise database queries, and use streaming SSR to send HTML before slow data queries complete.
Does TTFB affect Google rankings?
Indirectly — TTFB isn't a direct ranking signal, but it directly affects LCP, which is. Improving TTFB is one of the most leveraged LCP improvements because every millisecond saved in server response reduces LCP by the same amount.
Monitor Core Web Vitals continuously
AuditJet tracks every metric on a schedule and alerts you when scores regress — with revenue impact in dollars and AI fix suggestions.
Start Monitoring Free