sensible-browser - sensible web browsing
sensible-browser url
sensible-browser make sensible decisions on which web browser to call. Programs in Debian can use this script as their default web browser or emulate their behavior.
Documentation of behavior of sensible-utils under a debian system is available under section 11.4 of debian-policy usually installed under /usr/share/doc/debian-policy (you might need to install debian-policy)