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Time to First Byte (TTFB)

Time to First Byte is the wait between clicking a link and the first piece of the page arriving from the server. Until that first byte shows up, the browser has nothing to work with, and the screen stays as it was.

Why it matters

Section titled “Why it matters”

Everything else waits for this moment. Text, images and layout can only start once the server answers, so a slow TTFB pushes back everything that follows, including First Contentful Paint and Largest Contentful Paint.

A fast TTFB doesn’t make a page fast on its own. It only means the page isn’t held up before it has even started.

What influences it

Section titled “What influences it”

Cache: The most common cause of a slow TTFB on WordPress sites is a missing page cache. Without one, WordPress builds every page from scratch for every visit: it starts PHP, loads the plugins and the theme, and asks the database for content before it can send anything. With a page cache, the server hands out a finished copy instead. Logged-in visitors and pages like the cart usually skip the cache, so they stay slower even on a well-cached site.

Network: Redirects, for example from http to https or from a domain without www, each add a round trip. So do looking up the domain name and setting up the secure connection, all before the request reaches your server.

Server: How powerful the server is and how busy it is. On shared hosting, other sites compete for the same processors. An old PHP version or a missing OPcache makes every uncached page take longer.

WordPress: How much work it takes to build the page: many or heavy plugins, slow database queries, a large bundle of autoloaded options.

CDN: A CDN can answer from a server close to the visitor. If it has a cached copy of the page, both the distance and the work on your server drop away.

In Permo

Section titled “In Permo”

Permo shows TTFB in the Real users section of the PageSpeed page: the value that 75% of Chrome visitors reached or beat over the last 28 days, and how many visits were good, needed improvement or were poor. Google only publishes these numbers for pages and sites with enough Chrome visitors, so smaller sites often don’t get any.

Permo looks at the server’s answer from two more angles, each with its own page:

  • Server response time in Google’s lab test. It leaves out redirects and connection setup.
  • Uncached server response time, measured by Permo itself from your own server, bypassing the page cache. It shows how long WordPress takes to build the page when no cached copy helps.
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