Google told publishers about 10 months ago that site owners and tool providers to get ready for a change in how Google Image search will be sending their referral URLs. Rather than Google Image search traffic coming from the google.com site, they wanted to change it to help webmaster understand their image search traffic. The said that the referral URL will change to images.google.com so your analytics tool can better track it.
“UPDATE: After testing and further consideration, we have determined that the best place to measure query and click traffic from Google Images is in the Search Console Performance Report. Accordingly, we will continue to use https://www.google.com (or the appropriate ccTLD) as the referrer URL for all traffic from Google Images, and will not be providing a Google Images specific referrer URL (images.google.com),” the company said.
The story was quietly updated and didn’t send out any update anywhere else about it. No mention was made on their blog, nor on Twitter. Even in that case, AJ Kohn posted about it on Twitter: