Works great in Ubuntu 17.10 with Chrome and Firefox. With Chrome, it adds an icon to the menu bar to connect to https://extensions.gnome.org . With Firefox, this has to be done manually, AFAIK. FYI,

dpkg --list | egrep "chrome|firefox"
ii chrome-gnome-shell 9-0ubuntu1 all GNOME Shell extensions integration for web browsers
ii firefox 57.0.1+build2-0ubuntu0.17.10.1 amd64 Safe and easy web browser from Mozilla
ii firefox-locale-en 57.0.1+build2-0ubuntu0.17.10.1 amd64 English language pack for Firefox
ii google-chrome-stable 63.0.3239.108-1 amd64 The web browser from Google