How it works
When someone opens your page, the browser sends a request to your server. The server prepares the page and starts sending it back. Time to first byte, often shortened to TTFB, is the wait between the request and the first piece of the answer arriving.
That wait includes a few things:
- setting up the connection, including the secure part that comes with HTTPS
- any redirect on the way to the final address
- the server building the page
A common guideline is to stay under roughly 800 milliseconds, which is 0.8 seconds.
An example
Think of a restaurant. Time to first byte is the wait between placing your order and the first plate reaching the table. The rest of the meal can only follow after that.
A page works the same way. If the server needs two seconds before it answers, the screen stays blank for those two seconds, however light the page is.
Why it matters
- Everything else waits for it. Text, images and styles cannot appear before the first byte arrives.
- It affects other speed measures. TTFB is not one of the Core Web Vitals, but a slow start makes it harder to pass the one that measures loading.
- It can slow crawling. When a server answers slowly, search engines may visit fewer pages. That matters mostly on large sites.
How to check yours
- Open PageSpeed Insights, a free speed test from Google, and enter the address of your page.
- Look for Time to First Byte or server response time in the results.
- Compare the value with the 800 millisecond guideline. Run the test a few times, because the number varies.
- If it stays high, check the cache setting in your site builder, or ask your host what they can do.
The other parts of a healthy site are covered in the Technical SEO series. The free audit checks a live page for the essentials.