Reduce server response times (TTFB)

This means that the URL in question has a Time-to-First-Byte (TTFB) greater than 600ms.

Why is this important?

TTFB is a measure of how long it takes to receive data from the server, and slow server response times are one possible cause for long page loads.

When users navigate to a URL in their web browser, the browser makes a network request to fetch that content. Your server receives the request and returns the page content. The server may need to do a lot of work in order to return a page with all of the content that users want. For example, if users are looking at their order history, the server needs to fetch each user's history from a database, and then insert that content into the page.

Optimizing the server to do work like this as quickly as possible is one way to reduce the time that users spend waiting for pages to load.

What does the Hint check?

This Hint will trigger for any internal HTML URL that takes more than 600ms for the server to respond to the main document request.

How do you resolve this issue?

The first step to improving server response times is to identify the core conceptual tasks that your server must complete in order to return page content, and then measure how long each of these tasks takes. Once you've identified the longest tasks, search for ways to speed them up.

There are many possible causes of slow server responses, and therefore many possible ways to improve:

• Optimize the server's application logic to prepare pages faster. If you use a server framework, the framework may have recommendations on how to do this.
• Optimize how your server queries databases, or migrate to faster database systems.
• Upgrade your server hardware to have more memory or CPU.

Further Reading

• Reduce server response times (Lighthouse documentation)
• What Is Time To First Byte, And How To Improve It
• How to optimize Time To First Byte (TTFB)