There are two ways to load a webpage’s scripts: Synchronously and Asynchronously. This includes the scripts used for AB Testing, such as the Convertize Pixel. Here, we will describe the difference between synchronous and asynchronous loading, and explain why the Convertize Pixel loads synchronously by default.
By specifying that a script should load asynchronously, multiple scripts are loaded at the same time, rather than in sequence. The advantage of this is that it allows a page to load more quickly. However, it can cause a flickering effect in which the user sees one version of a page before the variation is loaded.
With synchronous loading, a webpage’s scripts are loaded in sequence. This can cause the page to load more slowly, but prevents the errors caused by asynchronous loading.
The Convertize pixel loads synchronously in order to ensure the best user experience possible. Unlike with asynchronous loading, the user does not encounter a flickering effect. In order to ensure the fastest possible loading times, Convertize introduced Lightning Mode.
It is also possible to make a change in the script in order for it to load asynchronously. The instructions for this can be found in our guide to making the Convertize pixel asynchronous.
NB: Tag Managers do not support synchronous loading scripts. This is why using a Tag Manager to implement Convertize pixel will not give the best user experience.