Time to Interactive

Time to interactive (TTI) is a metric that measures how long it takes a page to respond to user interactions without lag. It indicates how long a website needs to process input from users. The TTI is one of many metrics used to measure the loading time of a website that corresponds to usage, therefore relevant to the user experience.


There are many ways of determining the loading time of a web page. Many of these methods, such as time to first byte, are not very accurate. A website’s JavaScript may have already loaded, but it is not yet ready to process user input. The metric Time to interactive (TTI) is used to determine the moment when a website is really available to the user, and the Speed Index is used to take into account the loaded visible elements on a page.

Time to interactive is a metric intended to give developers and webmasters an alternative to conventional loading time. It has not yet been standardized, but is used in tools such as Lighthouse. Google wants to standardize this metric in the future.[1]

Prerequisites for determining the TTI[edit]

  • The website has displayed useful content. In the Lighthouse tool, the metric "First Contentful Paint" is also used here.
  • Event handlers have been registered for most visible page elements. In practice, this means that necessary JavaScript or clickable elements have been loaded and are ready for user input.
  • The page reacts consistently within 50 milliseconds to user input. Thus, all important scripts are loaded and do not generate a long pause after user input.

The TTI is measured on the basis of the RAIL model. [2]This is a performance model for websites. The acronym "RAIL" stands for "Response", "Animation", "Idle" and "Load".

Optimization of the TTI[edit]

There are different ways of optimizing the TTI of a website:

  • Unused scripts are not loaded. Ideally, only sources that are necessary for the optimal user experience are loaded.
  • Each script is loaded only once
  • The loading time of resources can be reduced through compression

Advantage for SEO[edit]

The TTI is a non-standardized measure used to measure how ready a website is for user input, and therefore interactivity. It is useful for search engine optimization, in particular through its role in improving the user experience. However, it should be taken into account that the TTI is only a theoretically determined metric, and can only give an approximation of the expected user experience. For example, the TTI does not replace user experience tests that are carried out with real people in the context of usability testing.


  1. A Technical SEO Guide to Lighthouse Performance Metrics searchenginejournal.com Accessed on July 9, 2019
  2. RAIL developers.google.com Accessed on July 2, 2019.

Web Links[edit]