gnome-shell
I have switched over to GNOME Shell, and use GNOME Shell Extensions to tweak the looks and functionality of my distribution.
However, I have not yet found out what technology is used to install, enable and disable the extensions from the webpage with just a few clicks.
How is it implemented? Can any webpage do this?
Chrome and Chromium dropped support for the NPAPI plugins (Netscape Plugin Application Programming Interface) in favor of PPAPI (Pepper Plugin Application Programming Interface) so all plugins that use NPAPI (like GNOME Extension plugin) are just not supported.
The only alternative is using another browser that allows them (like Firefox) or asking the developers to move to PPAPI (unlikely).
NOTE: This is the blog post from the Chromium blog mentioning this, titled: Saying Goodbye to Our Old Friend NPAPI.
gnome-tweak-tool
Best Answer
It is implemented using a browser plugin. "Gnome Shell Integration".
Try disabling it (firefox: addons -> plugins) and it no longer works.
Only the gnome website can use it.