If your website use sources from external sites (read: something that is loaded from the cloud) then your visitor's browser will retrieve those sources directly from those external servers.
Those external services can therefore collect the IP addresses of your visitors.
Think about:
- JavaScript libraries like JQuery,
- CSS libraries like Bootstrap
- Webfonts like Google fonts
- Javascript applications like chat service, currency convertors, the weather, etc
Measure: download the external sources, add to your local website and change all HTML/PHP scripts in your website to use the local services instead
