Domain Categories are used on the domain registration page (cart.php?a=add&domain=register) to  group domain TLDs into categories such as Popular, Shopping, or  Real Estate. This makes it easier for clients to navigate and find their ideal domain extension:

The categories under which TLDs are listed can be customised by creating a file specifying the desired category. New and specialised TLDs can be also be categorised.

This is a simple 3-step process:

1. Begin by creating a custom categories.json file.

2. Using your preferred code or text editor, define the domain categories you wish to use in a JSON array format. For example:

3. Upload the file to your WHMCS installation's /resources/domains/ directory.

The changes will take effect immediately and the domains are now be categorised as defined in the file.

To learn more about the domain categories overrides file, including how to remove TLDs and categories, refer to the Domain Categories Documentation.