Perceived speed is the speed that humans experience when using a website or app. That is something performance tools cannot evaluate.
Here are some examples of ‘perceived speed’
Google’s Core Vitals
The introduction to Google’s Core Vitals had percisely to do with getting an understanding of the human experience.
It used to be at some point, where Google only cared about speed, and not about perceived speed. That had drawbacks. It meant people can optimize their site by twisting up every dial, and while users had an uncomfortable experience, search engines rewarded them for it.
With the introduction of CLS, FCP, and LCP, you couldn’t trick Google anymore.
It is possible to make a site load very fast, but end up with flashes of the screen during page load, creating a poor experience. Hence lots of testing is needed.
CLS calculates the amount that pixels or objects moved or transformed above the fold when a page loads.
A method used to increase perceived speed is by implementing link preloading. Making a future page fetch resources before a user clicks on it. Read more about Link Preloading
Page Loader Animations
Animations keep a user engaged during extended load times. Such as colorful spinners and fades. That lets your application buy some time to render things without giving the user an uneasy screen.
Search engines know that the duration of an engagement with a user is more important than how fast a page loads. The time users spend on a page from a search result relative to other results for that query is the metric that matters most in the end.
Perceived speed is not how fast your website or application loads but rather the human experience.