Assuming you are using our JavaScript Tracker you can remove the domain from the tracked URL by adding this to your tracking code:

_paq.push(['setCustomUrl', window.location.pathname.substr(1) + location.search]);

This way only the path and URL parameters are being tracked and reported in Matomo.

Note: We have an alternative FAQ if you would like to hide the Matomo URL from the front-end instead.

Previous FAQ: How do I enable Secure cookie flags in all tracking cookies?