There are tons and tons of complaints and concerns posted in the Google Webmaster Forums and posted on Twitter and Google+ about the Google Search Console showing huge drops in the index counts in the Sitemaps report.
Here is a sample report I pulled from one of the profiles I have access to:
You can see on July 14th the index count dropped significantly, in this case by almost 3,000 pages.
Here is another screen shot, showing a drop of around 150,000 indexed pages!
I asked Google's Gary Illyes about this and he responded on Twitter saying it is a known bug that Google is addressing.
@rustybrick if that was a question, then yes, it's confirmed and we're working on it :)
— Gary Illyes (@methode) July 17, 2015This is not uncommon for the Google Search Console, formerly Google Webmaster Tools, reporting interfaces to have glitches. But this one is one of the more serious ones.
If you see your page count drop like this in Google Sitemaps reporting, you are not alone, Google is working on fixing it.
Forum discussion at Google Webmaster Forums, Twitter Google+ and Gary on Twitter.
