Time To First Byte

Time To First Byte

The world of technology is constantly changing and challenging us with new developments. Currently, the most pressing issue is Time to First Byte (TTFB). 

This concept may not be familiar to many, but it is one of those that define the path of your website’s performance. Today, TTFB has transformed into an inseparable metric, defining key user metrics. 

In this article, let’s set aside the mysteries, and dive straight into the details of TTFB.

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What is Time to First Byte?

Time to First Byte, often abbreviated as TTFB, represents the time taken from a user’s browser request to receiving the first byte of data from the server. 

It’s a significant part of web performance analysis and greatly affects how quickly your webpage loads on a user’s device. 

TTFB is a web server’s speed metric, which gives an indication of the web application’s responsiveness. It measures the duration from the user or client making an HTTP request to the first byte of the response being received by the client’s browser. 

This time duration is the sum of three main components:

  1. DNS Time - time that it takes to complete the DNS resolution for the required domain
  2. Connection (including TLS Handshake) establishment
  3. Wait Time to send the request itself and receive the response.


The Impact of Time to First Byte on User Experience

TTFB has a tremendous influence on user experience as it directly correlates to the loading speed of your website. A faster TTFB means your site appears to load quickly, which is a key metric in improving user satisfaction. 

But why does this matter? In today’s digital world, where user attention spans are decreasing, every millisecond counts. According to recent studies, the average human has an attention span of just 8.25 seconds - 4.25 seconds less than in the 2000s. 

If your site takes too long to load, users might lose patience and abandon the page, negatively impacting your site’s bounce rate, SEO, and ultimately your revenue. 

In fact, a study by Amazon discovered that as page load time increases by 100ms, their revenue took a 1% hit. That’s a massive impact on user behavior triggered by a minor fraction of a second delay!

How To Measure TTFB?

Fundamentally speaking, if you - as a site owner, or a user seeking to understand a website’s performance, doesn’t know how to measure or calculate TTFB, then the metric is valueless for you. 

Therefore, let’s simplify this process, and break it down into two primary methods that can enable you self-calculate your website’s Time to First Byte:

Using Online Tools

For those who prefer an alternative to browser developer tools, several online services can measure Time to First byte. Tools like WebPageTest or Pingdom are easy to use, and offer a comprehensive performance analysis of your website, including TTFB.

Here’s a simple process for using WebPageTest:

  1. Navigate to WebPageTest (
  2. Enter the URL of the website you want to test. 
  3. Select the location and browser you want to use for the test. 
  4. Click on ‘Start Test’. 

Once the test is completed, you’ll receive a detailed report about the website’s performance, including TTFB. This will be listed under ‘First Byte Time’ on the ‘Performance Results’ page. 

Google recommends keeping TTFB under 200ms. This might seem ambitious, but it’s extremely important. Google has also offered their own tool called PageSpeed Insights to enable websites to attain this mark!

Monitoring, Synthetic Checks, and Real User Monitoring (RUM)

Consistent and high-quality user experience is a non-negotiable aspect of running a successful online platform, no matter where in the world users are located. 

While each method has their benefits and drawbacks, when they complement each other together, they become an extremely powerful solution!

This makes monitoring - including synthetic checks and Real User Monitoring (RUM) - not just an option, but a critical requirement for businesses with a global footprint.

  1. Real User Monitoring (RUM): This is a method to analyze a user’s interaction with a website or application in real time, providing insights into their experience and the performance of the platform.

    However, it’s important to note that RUM results can indicate end-user network disruptions that are unrelated to the performance of the CDN network or the origin.
  2. Synthetic Checks: These are automated tests performed by a Content Delivery Network (CDN) to verify the availability and performance of web applications. Synthetic checks mimic user behavior to ensure that web applications are functioning as expected, catching potential issues before real users face them.

    While synthetic checks are an excellent method for verifying availability, it’s crucial to understand that the file selected for performance testing can greatly influence the results.

    So, if you’re using a JSON file origination from the source, or a simple static image retrieved from the CDN’s cache storage, both reflect the performance of the CDN and the origin. This is especially true since the synthetic checks are dispatched from an internet server. 

Monitoring equips us with crucial performance data, while synthetic checks simulate user requests, identifying potential issues. On the other hand, RUM gives a real-time perspective of user interactions, helping to uncover unexpected patterns or bottlenecks affecting TTFB. 


Factors Affecting Time to First Byte

Understanding what contributes to a slow TTFB is the first step towards optimizing it.

These factors are mostly website specific, but there are a few distinct cases that are generally the culprit of a low Time to First Byte test score:

  • Network Latency: The physical distance between the server and the user causes a high TTFB, the larger the distance, the higher your TTFB.
  • Server Performance: If your server is slow or overloaded with requests, it will take longer to respond. 
  • DNS Performance: Translating your site’s domain name into an IP address, which is a process that takes time. If your DNS server is sluggish or poorly configured, it can significantly increase the TTFB. 
  • Website Configuration: Your website’s setup and coding can also impact TTFB. For example, large high-resolution fonts and images can increase TTFB as they require more data to be transmitted, especially if not properly optimized or compressed. Therefore, any delay in retrieving data from your site’s databases can increase TTFB. 
  • Content Delivery Network (CDN): Not using a CDN or having one with sub-optimal configuration can increase TTFB, particularly for remote users. The TTFB is influenced by the efficiency of your CDN’s cache offloading and its overall speed performance. 


In summary, your Time to First Byte (TTFB) is a key player in website performance and has a profound impact on your website’s user experience, SEO, and revenue generation.

Monitoring TTFB is crucial for visibility into site performance and identifying improvement areas. Regular analysis promotes continuous enhancement of this vital metric, ensuring superior user experience. 

While improving TTFB requires a well-structured strategy, it’s an important step to take. After all, a swift, responsive website not only delights users but also has a direct impact on business outcomes. 

Published on:
April 3, 2024
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