Time to First Byte (TTFB): What Is It and What Affects It?
Time to First Byte (TTFB) is a metric used to determine how quickly a web server responds. It measures the time between establishing a connection to a server and beginning to download the content of a web page.
Connecting to a web server is a multi-step process, where each step can potentially introduce delays. When a website is slow or unresponsive, identifying the exact source of the slowdown is key to improving the user experience.
TTFB helps organizations identify weak points in the connection process. By determining where delays occur, companies can make changes to deliver their services faster and more reliably. Since site speed can affect search engine rankings, optimizing TTFB has become essential for both performance and visibility.
What Affects TTFB?
TTFB is influenced by three core actions:
Sending a request from the client machine to the server
Processing the request on the server and generating a response
Sending the response from the server back to the client
Action 1: Sending the Request to the Server
The measurement of TTFB begins with the request. The time it takes for the server to receive this request can vary based on factors like DNS lookup time, the speed of the user’s network, distance from the server, and any disruptions in the connection. While organizations have no control over the connection between the user and the internet, any delay in this step still impacts TTFB.
Action 2: Processing and Generating the Response
Once the server receives the request, it needs to generate a response. This involves triggering processes, querying databases, executing web scripts, and communicating with other systems on the network. Common strategies to reduce TTFB include caching web pages, optimizing server-side code, and improving hardware resources.
Action 3: Sending the Response Back to the Client
After the server generates a response, it must send it back to the user. This step depends on both the server’s and the user’s connection speeds. TTFB is measured the moment the client begins to receive the response—when the very first byte arrives. Transmitting a request and response over the network can account for nearly 40% of the total TTFB.