Starting December 1, Google has lost data in the Google Search Console’s search analytics and performance reports. According to Google, image search data was lost due to a bug, and it isn’t clear how much data was lost over what period of time. So far, we know that if you filter your search analytics and performance reports by image search, it may be missing some reporting data as of Dec 1.
Google posted on the data anomalies page, “December 1 onward: Some data for clicks in Google Images from mobile devices was dropped. This change only affects Search Console reporting, not your actual performance on Google Search.”
This was confirmed by John Mueller from Google that this was a bug and not an intentional change to how Google reports on image search.
No, just an unfortunate bug. :-/
— 🍌 John 🍌 (@JohnMu) December 4, 2018
So if you’re looking through your search analytics and performance reports in Google Search Console and you notice that there is a dip in traffic and impressions, there’s a chance that it is related to this bug. By further filtering on image search, you should be able to see the extent of the data issue.
Google did add, “This change only affects Search Console reporting, not your actual performance on Google Search.”