Time to Interactive (TTI)

May 20, 2023

Time to Interactive (TTI) is a performance metric used to measure the time it takes for a web page to become interactive. It is the time between the start of the page load, and the moment when the page is fully loaded and the user can interact with the content of the page. TTI is one of the key metrics used by web developers and website owners to measure the usability and user experience of their web pages.

TTI focuses on the user’s perspective, indicating how long a user must wait before being able to interact with a webpage. It is different from other metrics like First Contentful Paint (FCP) or Largest Contentful Paint (LCP) that measure the time it takes for specific content to appear on the page.

Purpose and usage

The purpose of TTI is to measure the time it takes for a website to become responsive, i.e. when the user can interact with the page, click on links, fill in forms, or perform any other action. The longer the TTI, the more frustrating the waiting experience will be for the user, leading to a higher bounce rate and lower user engagement.

TTI is a key metric for website owners and developers to measure the performance of their web pages and to identify areas for improvement. By monitoring TTI, web developers can identify performance bottlenecks and optimize various aspects of the web page, such as server response time, script execution time, and resource loading time.

In addition, TTI is a part of the Core Web Vitals, a set of performance metrics developed by Google that are used to measure the user experience of web pages. Websites that meet the Core Web Vitals benchmarks are more likely to rank higher in Google search results, making TTI an important metric for search engine optimization (SEO).

Calculating TTI

The calculation of TTI depends on the user’s interaction with the page. The following steps are taken to calculate TTI:

  1. The browser starts loading the page and all its resources, including HTML, CSS, JavaScript, and images.

  2. The browser parses the HTML code and constructs the Document Object Model (DOM) of the page.

  3. The browser downloads and executes all the JavaScript code on the page.

  4. The browser constructs the Render Tree, which is a visual representation of the page that includes all the visible elements, such as text, images, and videos.

  5. The browser paints the content on the screen, and the user can see the page.

  6. The user can interact with the web page, such as clicking on links, scrolling, or filling in forms.

The time it takes for the user to interact with the web page is the TTI.

Optimizing TTI

Optimizing TTI requires optimizing different aspects of a webpage, including server response time, resource loading time, and script execution time. The following are some tips to optimize TTI:

  1. Reduce server response time: A fast server response time is critical to reducing TTI. Optimizing server response time may involve using a content delivery network (CDN), caching, and compressing files.

  2. Minimize resource loading time: Resources such as images, stylesheets, and scripts can significantly increase TTI. Optimizing resource loading time can be done by minimizing the number of requests, compressing files, and asynchronously loading resources.

  3. Optimize JavaScript execution time: JavaScript code can cause performance bottlenecks, leading to a longer TTI. Optimizing JavaScript execution time may involve removing unused code, using efficient algorithms, and deferring non-critical JavaScript code.

  4. Use lazy loading: Lazy loading is a technique that delays the loading of non-critical resources until they are needed. This can significantly reduce TTI by reducing the number of requests made during the initial page load.

  5. Prioritize above-the-fold content: Above-the-fold content refers to the content that is visible to the user without scrolling. Prioritizing above-the-fold content can reduce the perceived TTI, making the page appear to load faster.

  6. Use a performance monitoring tool: Performance monitoring tools can measure and analyze the performance of a web page, including TTI. These tools can help identify performance bottlenecks and suggest optimizations to improve TTI.