The Time To First Byte involves many moving parts. TTFB is the time it takes for a server to send the first byte of data once your browser has made its initial HTTP request. This is a bit of an oversimplification, but it serves to illustrate the basic concept. When this time is a large part of the loading time of your website, it can often feel like the time should be much lower. Yet, there can be many functions that a web server does before responding with the first byte. A long TTFB does not usually indicate a problem. Sometimes your website may actually take longer to load if the TTFB was shorter. Other times, a TTFB time may be very short, but the server still responds slowly. But how can that be?
What are some things that can affect TTFB times?
A web server can provide a partial HTTP header before sending your website content. This can give a very short TTFB time, while your site may still take a long time to finish loading. Remember that the TTFB is only the time to the first byte of HTTP data, and not your website data.
Compression can also affect the TTFB of a website. Your server may be setup to compress your website content before sending its data to a web browser. This can make the TTFB longer, while your site still loads faster than with no compression.
So, does the TTFB of my site matter?
The time-to-first-byte can be helpful in addressing potential page load bottlenecks. However, it’s key to remember that a short, or even a long TTFB does not by itself confirm a misconfiguration. There are more factors that affect loading time such as connection latency, if you use caching or not, and so on. But these examples show some of the misconceptions of blaming TTFB for a slow website.