TL;DR: The perceived loading time is what shapes the user’s impression of the speed of a website, but measuring perceived loading time is difficult. There are technical loading times available but it is not clear if these times can be used in any meaningful way. This master’s thesis verified whether the perceived loading time can be easily correlated with any technical loading time, such as FirstPaint for instance. The result shows that a page with a fast loading time from a technical point of view is not necessarily perceived as fast by the user and vice versa. Therefore it is not sufficient to rely only on technical measurements and disregard the user’s perception.

Client-side performance is a big deal. There are various studies on the relationship between loading time and critical success factors such as usability of online shops, customer loyalty and sales. Yet a page with an objectively long total loading time could still be perceived as fast by the user, as the visible part of the browser window has already loaded and invites the shopper to interact with the page.