Cross domain tracking
Default settings from Brave browser has 3rd party cookies disabled. Which I am assuming also disables 3rd part storage like IndexedDB etc. Because of this protection it is not possible for a 3rd party to track users across multiple domains.
But, Even though third-party cookies is disabled by default using Shared workers, a third-party is able to track the user across domains and websites.
If you visit the these three pages in three tabs, you will notice that as a third-party it can learn the movement of a user across domains, even though the user has disabled 3rd party cookies.
The third party script is being loaded from https://konarkmodi.github.io/
Because of this protection it is not possible for a 3rd party to track users across multiple domains. The demo is not very clever, but a 3rd party with a large footprint on the web can use this to track substantial web browsing behaviour of the user.