Time to First Byte (TTFB)

Time to First Byte (TTFB) isn’t one of the Core Web Vitals, but it feeds into all of them. At Uxify, we use TTFB as a core checkpoint for diagnosing backend and network latency - especially when looking at poor LCP or slow regional performance.

TTFB measures the time between a user requesting a page and the first byte of response coming back from the server. It includes DNS lookup, TCP handshake, TLS negotiation, server processing, and network delays. It’s essentially the starting gun for page rendering - if TTFB is slow, everything else is stuck waiting.
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To deliver a responsive experience, the 75th percentile (P75) of Time to First Byte (TTFB) should be under 0.8 seconds. This ensures 75% of your users get a response from the server quickly. Here’s how Uxify categorizes TTFB performance:

Two words: users and Google. Let’s start with your users. A fast TTFB means less waiting, quicker load, and smoother interaction. When TTFB is slow, users feel the delay before anything even appears - and that sets a bad tone from the start.
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Then there's Google. While TTFB isn’t directly part of Core Web Vitals, Google does measure it and has flagged it as a contributing factor in page performance. More importantly, it’s tightly connected to LCP — a slow TTFB almost guarantees a slow LCP. So yes, fixing TTFB is critical to getting the rest of your vitals in shape.

Real User TTFB is collected from every pageview through the Uxify script, giving you a complete and unsampled view of how quickly your server responds to user requests. This dataset reflects the true backend performance your visitors experience - not just averages, but real latency by region, device, browser, and network conditions. Since Time to First Byte is often the first bottleneck in the loading chain, this metric is essential for diagnosing slow origins, CDN misconfigurations, or inconsistent caching strategies across your infrastructure.

This filter narrows the Real User TTFB dataset to only the URLs recognized by Google’s Chrome UX Report. It’s ideal when you want to validate or investigate why certain pages are underperforming in Google's Core Web Vitals reports, despite improvements in your own monitoring. By comparing TTFB for CrUX-covered URLs against Google’s sampled data, you can confirm whether slow server response is responsible for poor LCP or PLS scores - and take action with confidence.

Google CrUX TTFB comes from Chrome’s field data, sampled from real user sessions and aggregated into public datasets. While it doesn’t offer full visibility - only high-traffic pages are included - it’s still a vital signal. Google uses CrUX TTFB as part of its overall assessment of site performance and as a leading indicator of backend speed. It’s also a key contributor to your Core Web Vitals status, which affects SEO. Monitoring this data helps ensure your improvements in infrastructure are actually being reflected in Google’s view of your site.

Here are three of the most common and actionable reasons we see for high TTFB in Uxify Experience:

Uxify Experience gives you 80+ TTFB lenses across caching, location, traffic type, and more. Use it to zero in on backend bottlenecks. Then layer on Navigation AI or better CDN strategies to accelerate that first byte.