While software like NoScript prevents this, it's probably a good idea to block this protocol directly as well, just to be safe. Note: This disables browser-based call functionality that is used for webapps like Discord, Hangouts, Jitsi, etc.
In short: Set "media.peerconnection.enabled" to "false" in "about:config".
Explained:
If you want to make sure every single WebRTC-related setting is really disabled change these settings:
Now you can be 100% sure WebRTC is disabled.
Safari is far stricter with WebRTC than other major browsers, and it does not leak your IP address in its default configuration. If you'd like, you can follow these steps just to double-check your browser:
WebRTC cannot be fully disabled in Chrome; however, it is possible to change its routing settings (and prevent leaks) using an extension. Two open-source solutions include WebRTC Leak Prevent (options may need to be changed depending on the scenario), and uBlock Origin (select "Prevent WebRTC from leaking local IP addresses" in Settings).
Chrome on macOS and Internet Explorer do not implement WebRTC yet. But we recommend using Firefox on all devices.