When it comes to evaluating website performance, “Time to First Byte” (TTFB) is a metric that often comes up. It’s frequently referenced in discussions about website speed and user experience. But what exactly is TTFB, and how reliable is it as a performance indicator? In this article, we’ll break down what TTFB measures, explore its limitations, and discuss why it shouldn’t be the sole focus when optimizing your site’s performance.
What is TTFB?
TTFB stands for “Time to First Byte.” It measures the amount of time it takes for a user’s browser to receive the first byte of data from the server after making a request. This metric includes several key phases:
- DNS Lookup: The time it takes to translate the domain name into an IP address, so the web-browser can request the web-page from the server
- Connection Establishment: The time required to establish a connection between the client and the server, including the TCP handshake and, if using HTTPS, the SSL/TLS handshake
- Server Processing: The time it takes for the server to process the request, including querying databases, generating the page and compressing up the response
- Network Latency: The time it takes for the data to travel from the server to the user’s browser.
A practical demonstration of this can be seen when creating a PHP based webpage with a 5 second sleep in the code to simulate a server generating a complex page. The result when tested with a TTFB tool was a a TTFB of 5.279 seconds
The same test when loading a simple html file that did not need any processing had a TTFB of under 0.118 seconds
The Limitations of TTFB
While TTFB can provide insight into certain aspects of your website’s performance, it’s not without its limitations. Here are a few reasons why TTFB might not always be an accurate indication of overall site performance:
- Focus on Server Response: TTFB primarily measures server response time, but it doesn’t account for client-side performance factors such as rendering, JavaScript execution, or resource loading. A site with a good TTFB might still be slow to fully load if it has heavy client-side processing. This is particularly true on slower machines and mobile devices.
- Network Variability: Network conditions and latency can vary greatly between users and testing servers. A testing server in US will always show a high concerning number for a site hosted in Australia.
- Caching Effects: Caching mechanisms can significantly affect TTFB. If a resource is served from a cache, TTFB might be very low, but this doesn’t reflect the server’s actual response time for uncached requests.
- Misleading: TTFB is only a measure of just the first received byte of the http header, this was discussed in the Cloudflare Blog Post Stop worrying about Time To First Byte (TTFB) which explored TTFB can easily be manipulated and does not directly mean the site will load fast. For example a gzip compressed page which is significantly smaller will have a higher TTFB but may load significantly faster.
- Not Reflecting User Experience: TTFB is just one aspect of the user experience. A low TTFB doesn’t guarantee a fast-loading site. Other factors, like First Contentful Paint (FCP) or Largest Contentful Paint (LCP), often provide a better picture of how quickly users perceive a page to be loading.
Why TTFB Isn’t Always an Accurate Performance Metric
Given these limitations, it’s clear that TTFB is not always a reliable standalone indicator of performance. For example, a site with a high TTFB could still provide a fast, responsive user experience if the server delivers content efficiently after that initial delay. Conversely, a low TTFB might be misleading if the rest of the page takes a long time to load due to heavy resources or complex client-side processing.
In other words, TTFB is just one piece of the puzzle. Relying solely on TTFB can lead to a narrow view of performance, potentially causing you to overlook more critical aspects that impact the user experience.
Myth: But isn’t Low TTFB is required for SEO?
SEO myths often make our blood boil and are often baseless!
This belief was dispelled by John Mueller (Webmaster Trends Analyst at Google) on Twitter who advised they do not use TTFB for anything in search/ranking and to not blindly focus on metrics.
Google does however very much focus on ‘Page Loading Speeds’!
How to Improve TTFB (and Overall Performance)
Despite its limitations, improving TTFB can still contribute to better overall performance. Here are some strategies to consider:
- Optimize Server-Side Processing: Reducing the time the server takes to generate a response can lower TTFB. This might involve optimizing your websites code, streamlining or reducing database queries or upgrading to a faster server. Disabling and reducing the number of plugins is often the best way to achieve this on. Ensuring you are on the latest PHP version is another.
- Use Content Delivery Networks (CDNs): CDNs can cache and deliver content from servers closer to the user, reducing network latency and improving TTFB, particularly ‘proxying’ such as Cloudflare
- Implement Caching: Use caching to store frequently accessed data, reducing the time needed to process requests. Both server-side caching (like object or page caching) and client-side caching (using cache-control headers) can improve TTFB. WP-Rocket, W3 Total Cache or the Litespeed Cache Plugin are a must for WordPress
- Reduce DNS Lookup Time: Speed up DNS resolution by using a faster DNS provider or by caching DNS queries. KeyCDN has an excellent tool to test your DNS resolution speed from around the world. If your DNS is slow, consider Cloudflare for DNS.
- Use Keep-Alive Connections: Enable keep-alive connections to reduce the overhead of establishing a new TCP connection for each request, which can lower TTFB.
Conclusion
TTFB is a valuable metric for understanding certain aspects of server performance, but it should not be viewed in isolation. Its limitations mean it can be misleading and imply issues that do not exist.
If you enjoyed this article, you might also like our recent post ‘Performance Tips: How To Speed Up Your WordPress Website‘ .
What has your experience been with investigating TTFB issues? Let us know in the comments below