# How to unify Tracking ID prefix

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

Add in functions.php file of your theme:

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

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