It adds the Onion search engine to chrome without any popup. It is only compatible with chrome. Search on onionsearchengine.com
This extension for Chrome allows you to set the Onion search engine as the default search engine in browser and when you use keyword search directly on the Onion search engine.
Onion search engine allows you to search in the normal network as well as in the onion network.
In order to see the sites in the onion network you must use Tor or a VPN Tor that also allows you to browse anonymously.