The referrer URL is part of the HTTP header, and indicates the last page the user was on, and clicked, to visit the destination page.
The referrer URL is the way web analytics software tracks the source of a click to your website. Currently, there is no clear way to stipulate whether a user has originated from Google search, or Google Image search. To combat this, Google have opted to roll out a new referrer URL specific to Google Images which will be tested over the course of the next few months.
Speaking of the change, Google’s product manager Ashutosh Agarwal said:
“The referrer URL is part of the HTTP header, and indicates the last page the user was on, and clicked, to visit the destination webpage”
By changing it to https://images.google.com, users are able to better understand what traffic is coming to their site from Google Image search opposed to Google Search.
If you use Google Analytics to track website data and traffic, the new referral URL will be automatically ingested and users will be attributed to Google Images appropriately.