Total Blocking Time (TBT): Optimize your website’s performance

Optimize your website's performance by understanding Total Blocking Time (TBT). Learn how TBT affects user experience and search engine rankings.
Total Blocking Time

A fast and responsive website is essential in today’s digital landscape. Users expect instant access to content and a seamless experience, regardless of whether they visit your website from a computer, tablet or mobile device. Website performance therefore plays a crucial role in satisfying users’ expectations and ensuring their engagement.

Introduction to Total Blocking Time (TBT)

An important factor affecting website performance is Total Blocking Time (TBT). TBT refers to the time it takes for a website to respond to user interaction, such as clicking on links or scrolling down the page. The longer the TBT, the longer it takes users to experience interactivity and content on your website.

In this blog post, we will dive into the concept of Total Blocking Time (TBT) and its impact on website performance. We will take a closer look at the factors that affect TBT and how it can affect both user experience and search engine rankings. In addition, we will present strategies and best practices to reduce TBT and optimize your website’s performance.

Follow along and discover the importance of TBT optimization to create a better user experience and increase the success of your website.

Understanding Total Blocking Time (TBT)

A. Definition and meaning of TBT

Total Blocking Time (TBT) is an important measure of website performance that indicates the total time a website is blocked from interaction while loading and executing critical content. TBT includes the time it takes to handle and execute JavaScript, CSS og andre ressourcer, der er nødvendige for at vise indholdet på siden. En lav TBT betyder, at din hjemmeside reagerer hurtigt på brugerens handlinger, hvilket resulterer i en bedre brugeroplevelse.

B. Relationship between TBT and user experience

TBT has a direct impact on the user experience. When TBT is high, users experience delays and a sluggish response, which can lead to frustration and potentially cause them to leave the website. A low TBT ensures a more responsive website where content is displayed quickly and users can interact without delays. An improved user experience can increase engagement, extend visit time and increase the likelihood of conversions.

C. How TBT Affects Search Engine Rankings

Search engines like Google place great importance on the user experience, including fast loading time and responsiveness. TBT has become an important factor in search engine algorithms as it indicates how well a website delivers its content to users. Websites with a low TBT are more likely to rank higher in search results as they offer a better user experience. Therefore, optimizing TBT is essential to improve both user experience and search engine rankings.

Understanding Total Blocking Time (TBT) is crucial to optimizing website performance. By reducing TBT, you can create a faster and more responsive website that satisfies users and gets better search engine rankings.

Factors affecting TBT

A. Render-blocking resources

One of the primary factors affecting TBT is render-blocking resources. These resources, such as JavaScript and CSS files, can delay the loading and execution of critical content on a website. When render-blocking resources block the critical rendering path, it can result in high TBT. By identifying and managing these render-blocking resources, you can reduce TBT and improve performance.

B. Execution and Parsing of JavaScript

JavaScript is a powerful technology that adds interactivity to websites. However, complex JavaScript functions and scripts with long execution time can cause high TBT. Executing and parsing JavaScript can be time-consuming and block other processes on the website. Optimizing JavaScript code, minimizing and prioritizing critical JavaScript content can help reduce TBT.

C. CSS Rendering and Layout

CSS rendering and layout also play an important role in TBT optimization. When CSS rules and layout components are not optimally organized or contain complex calculations, it can delay the rendering and layout of the content on a website. By optimizing CSS code, reducing the number of CSS requests, and using efficient layout techniques, you can reduce TBT and improve user experience.

D. Impact of Third Party Scripts and Plugins

Third-party scripts and plugins, such as ads, chat boxes or social media integrations, can have a significant impact on TBT. These external scripts can delay the loading and execution of content on a website, especially if they are not optimized or loaded asynchronously. It is important to evaluate and optimize the use of third-party scripts and plugins to minimize their impact on TBT.

By paying attention to these factors and implementing relevant optimization methods, you can effectively reduce Total Blocking Time (TBT) and improve the speed of your website. Optimizing render-blocking resources, JavaScript execution, CSS rendering, and handling third-party scripts are important steps towards a more responsive and faster user experience.

Measurement of Total Blocking Time

A. Tools for measuring TBT

In order to optimize TBT, it is important to have reliable tools for measuring this metric. There are several tools and services that can help measure and analyze TBT on your website. Some of the popular tools include Google Lighthouse, PageSpeed Insights,WebPageTest and Chrome DevTools. These tools provide insight into TBT values ​​as well as other performance-related metrics useful in the TBT optimization process.

B. Interpretation of TBT Scores and Values

When you measure TBT, you will be presented with a numerical value that represents Total Blocking Time. It is important to be able to interpret this score and understand its significance to your website’s performance. Generally speaking, a lower TBT score means that your website responds more quickly to user interactions and offers a better user experience.

Threshold values ​​may vary depending on various factors such as user expectations, type of content and the industry in question. It is important to understand the recommended threshold values ​​for TBT in relation to your specific situation.

C. Common challenges in TBT measurement

Measuring TBT can be associated with certain challenges. First, TBT values ​​may vary depending on the user’s device, internet connection and server load. In addition, complex interactions and dynamic content on the website can affect the TBT measurement. It is important to be aware of these challenges and take them into account when interpreting the TBT results.

By using reliable tools, understanding TBT scores and thresholds, and being aware of common challenges in TBT measurement, you can get a more accurate assessment of your website’s performance and identify areas for improvement. Measuring TBT is critical to tracking your optimization process and ensuring that your changes have a positive effect on user experience and performance.

Strategies to Reduce Total Blocking Time

A. Minification and optimization of JavaScript and CSS files

An effective strategy to reduce TBT is to minimize and optimize JavaScript and CSS files. This can be achieved by removing unnecessary code, reducing file size and using compression techniques such as minification. By optimizing these files, you can speed up loading and execution, reducing TBT and improving performance.

B. Lazy loading techniques for images and videos

Lazy loading techniques are useful for reducing TBT, especially when it comes to images and videos on your website. By implementing lazy loading, you ensure that the media are only loaded when they become visible in the user’s field of vision. This helps prevent the media from blocking the critical rendering path and results in a lower TBT.

C. Asynkron indlæsning af scripts

By loading scripts asynchronously, you can prevent them from blocking the critical rendering path and negatively impacting TBT. Asynchronous loading allows scripts to be loaded in parallel with other resources, which improves the page’s response time and reduces TBT. Use techniques such as the async attribute or asynchronous loading through JavaScript libraries to implement asynchronous script loading.

D. Critical rendering path prioritization

By prioritizing the critical rendering path, you can ensure that important content and resources are loaded first and displayed to users as quickly as possible. Identify the elements necessary to build the first visible content on the page and ensure that they are prioritized on load. By focusing on critical content, you can reduce TBT and improve user experience.

E. Reducing server response time

Another important strategy is to reduce server response time. Optimization of server setup, caching techniques and use of CDN (Content Delivery Network) can all contribute to faster server response times. A low server response time ensures that content is delivered to users quickly, resulting in a lower TBT and better performance.

By implementing these strategies, you can effectively reduce Total Blocking Time (TBT) and improve your website’s performance. By minimizing and optimizing JavaScript and CSS files, using lazy loading techniques, asynchronous loading of scripts, prioritizing critical rendering path and reducing server response time, you can create a more responsive and faster user experience.

Best practices for TBT optimization

A. Optimization of third-party scripts and plugins

An important best practice for TBT optimization is to optimize the use of third-party scripts and plugins. Carefully review and evaluate the scripts and plugins integrated into your website and remove or optimize those that are not needed. Choose light and effective alternatives that do not cause unnecessary TBT. Also, regularly monitor the performance of third-party scripts and plugins to ensure that they do not adversely affect the TBT level.

B. Code splitting and packing for efficient loading

By implementing code splitting and packaging techniques, you can improve the loading of your JavaScript code. Splitting code into smaller modules and loading only the necessary content based on user interactions can reduce TBT. Using bundling tools and technologies like webpack or rollup can help package and deliver code more efficiently.

C. Caching and Compression Techniques

Implementing caching and compression techniques is another important best practice for TBT optimization. Caching of static resources such as images, CSS and JavaScript files can reduce the load on the server and speed up loading time. In addition, using compression techniques such as GZIP can reduce file size and thus improve load time and TBT.

D. Implementation of resource hints and preloading

Resource hints and preloading techniques can be useful to improve load time and reduce TBT. By identifying critical resources, you can add resource hints like pre-fetching or preloading that indicate important resources to be loaded in advance. This can reduce waiting time and improve response time to user interactions.

E. Regular Monitoring and Performance Audits

Finally, it is important to maintain regular monitoring and perform performance audits of your website. This involves using tools to measure TBT, monitor performance and identify areas of high TBT. By conducting regular performance audits, you can identify and correct any TBT-related issues, optimize your website’s performance, and ensure a positive user experience.

By implementing these TBT optimization best practices, you can improve your website’s performance, reduce TBT, and ensure your visitors experience a fast and responsive user experience.


Optimizing Total Blocking Time (TBT) is critical to improving your website’s performance and user experience. TBT is a measurement of the amount of time your website is blocked from interaction, and a high TBT can lead to slow loading and delays in the user experience. By reducing TBT, you can create a more responsive website that delivers content quickly and satisfies user expectations.

In this blog post, we have explored several strategies and best practices to reduce Total Blocking Time (TBT). We’ve highlighted the importance of optimizing third-party scripts and plugins, applying code splitting and packaging, implementing caching and compression techniques, using resource hints and preloading, and performing regular monitoring and website audits. These strategies are designed to improve load time, reduce TBT and create a more responsive website.

Now that you have learned the importance of TBT optimization and the various strategies and best practices, it is important to take action and implement these methods on your website. Start by evaluating your website for TBT-related issues using measurement tools and performing performance audits. Identify the areas where TBT can be improved and begin implementing the recommended strategies and best practices. By prioritizing TBT optimization, you can create a better user experience, increase your website’s efficiency and achieve better search engine rankings.

Take action today and start improving your website’s performance by reducing TBT. Your efforts will not only benefit users, but also help build a stronger online presence for your business or organization.

Additional resources

A. Links to useful tools for TBT measurement and optimization

To help you measure and optimize Total Blocking Time (TBT), we’ve put together some useful tools to support you in this process:

Google Lighthouse:: A tool that provides a comprehensive analysis of performance and provides TBT metrics as well as recommendations for improvement.

  1. Link: Google Lighthouse

PageSpeed ​​Insights: A tool from Google that analyzes a website’s performance, including TBT metrics, and provides optimization suggestions.

  1. Link: PageSpeed Insights

WebPageTest: A free online tool that provides detailed performance analysis, including TBT metrics, and the ability to compare performance across devices and locations.

  1. Link: WebPageTest

B. Recommended articles, guides and tutorials on TBT optimization

If you want to dive deeper into the topic of Total Blocking Time (TBT) and learn more about effective optimization methods, we recommend the following resources:

“The Cost of JavaScript in 2019” by Addy Osmani: A detailed article that explores the importance of JavaScript performance and provides practical tips to reduce TBT.

  1. Link: The Cost of JavaScript in 2019

“Web Vitals” by Google Developers: A comprehensive guide to Core Web Vitals, including Total Blocking Time (TBT) and how to measure and improve them for a better user experience.

  1. Link: Web Vitals

“Optimizing for Total Blocking Time (TBT)” by Patrick Hulce: An in-depth article that explores strategies for optimizing Total Blocking Time and improving performance.

  1. Link: Optimizing for Total Blocking Time (TBT)

These resources can provide you with additional insight and guidance on TBT optimization and help you improve your website’s performance. Use them as a reference to improve your skills and continue to achieve better results.

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