Client-side testing

A method of dynamically modifying the content displayed to the user via JavaScript scripts executed directly in the browser. This approach is ideal for rapid testing of visual or textual elements, thanks to its great flexibility and simplified implementation, with no need to modify server code.

On the other hand, it can degrade site performance (loading time, visual stability), with a measurable impact on indicators such as First Contentful Paint (FCP), Largest Contentful Paint (LCP), Time to Interactive (TTI), Cumulative Layout Shift (CLS ) and Total Blocking Time (TBT).

We therefore recommend reserving this method for temporary experimentation, and then integrating the validated changes directly into the source code or on the server side.