> For the complete documentation index, see [llms.txt](https://ctracker-docs.keywordrush.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://ctracker-docs.keywordrush.com/how-to/how-to-unify-tracking-id.md).

# How to unify Tracking ID prefix

If you use the same Publisher ID on several WordPress installs (separate domains, subdomains, or subdirectories), you must use a unique tracking prefix for each site.

Add the following to your theme's `functions.php` file:

```php
function my_cbtrkr_subid_prefix()
{
    return 'yourprefix';
}
add_filter('cbtrkr_subid_prefix', 'my_cbtrkr_subid_prefix');
```

Please use only letters `(a-z)` for the prefix.