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Server response time in PageSpeed Insights (lab test)

Server response time is how long your server took to answer when Google’s lab test asked for the page: from the moment the request went out until the first byte of the page came back. It’s measured once per test, for the page itself, not for images or other files.

Why it matters

Section titled “Why it matters”

Nothing else can start before the page arrives. Every image, stylesheet and script is listed in the page, so the browser only learns about them once the server has answered. A slow response pushes back First Contentful Paint, Largest Contentful Paint and everything after.

This value is narrower than Time to First Byte. It leaves out redirects, looking up the domain name and setting up the connection, and it comes from a single test rather than from real visitors. It does include the trip from Google’s data center to your server and back, so a server far away from the test location starts with a disadvantage.

What influences it

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Cache: The most common cause of a slow server response on WordPress sites is a missing or expired page cache. Google’s test arrives like a first-time visitor, without cookies. If a cached copy of the page exists, the server can send it right away. If not, WordPress has to build the page first. A cache that was cleared shortly before the test, for example after an update, has the same effect.

WordPress: When WordPress builds the page, everything adds up: loading the active plugins and the theme, the database queries for the content, a large bundle of autoloaded options, and calls to other services that a plugin makes while the page is built.

Server: How powerful the server is, how busy it is at that moment, and how well PHP and the database are set up. On shared hosting, other sites compete for the same resources. An outdated PHP version or a missing OPcache makes every uncached page slower.

Network: Google runs the test from a data center in North America, Europe or Asia. The farther your server is from it, the longer the request and the response travel.

CDN: A CDN that caches whole pages can answer from a location close to Google’s test machine, without asking your server at all.

In Permo

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Permo shows this value on its PageSpeed page under Processing and test machine, in the first row. It’s Google’s measurement from the lab test.

Permo looks at the server’s answer from two more angles:

Reference values

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Lighthouse’s insight “Document request latency” flags a server response that takes longer than 600 ms. Google sets this lower than the 800 ms it recommends for Time to First Byte, because TTFB also includes redirects and connection setup (source: Chrome for Developers, Document request latency, accessed October 16, 2026).

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Sources