Where is Google Aggregating Reviews From?

[consultant]

Can anyone confirm all the sources Google is aggregating reviews from? I heard, and it looks like other than Google itself, they are scraping reviews from Yelp and possibly Facebook to include in the total number of reviews for a GMB listing?

 

[JoyHawkins]

The total number of reviews you see on an GMB listing is only based on Google reviews, not 3rd party reviews.