According to Moz.com, arguably the #1 authority on search engine optimization, review signals ranked 5th among the most important search engine ranking factors.
Factors of the reviews include:
- Review Quantity
Simple: more is better. - Review velocity
This needs to look legit and human. Too fast (too many too quickly) is more likely to be seen as faked “SERP-spam” and can damage your score. The ideal is slow and steady – just use real-world reviews and you’ll be fine. - Reviews Diversity
How many sites are pointing back to your core “money domain” i.e. the main website, and do those sites have reviews? If they do, it’s even more likely to be taken as legitimate non-faked, non-spam and thus trustworthy and as a result, worthy of ranking higher in the search engines. Note you could technically “spoof” and de-SEO some competitor, but we strongly don’t recommend this – (A.) they can use “disavow” to protect themselves, and (B.) it creates bad karma, and (C.) creates an arms race where they will likely notice, and trace it back to you. All that said, reviews on a wider array of websites is more likely to be legit and thus worthy of ranking higher. - Non-Google-Owned reviews with links and ideally addresses.
In short, the above applies here, but google properties and on-site reviews are counted differently than off-domain reviews specifically on properties not owned by Google (i.e. Facebook, Yelp among others) - Authority of those sites…
Grandma’s blog doesn’t count as much as Facebook. - Overall velocity off-domain
In short, the real-world is slower and more consistent and a bit messy. Faked/spammed is short-lived, and a bunch all at once. - Volume of testimonials
This comes back to “rich snippets” i.e. microformat stars - Google Maps Direct Reviews
Google Maps reviews for local businesses with review text - Authority Reviewers
Yelp, for example, doesn’t even show any of your reviews until you have published at least 5 reviews total (for 5 different businesses). This helps cut down spam on their side; authority reviewers have a lot of cross-linking (many links back to their reviews-list-page, which in turn means more indirect backlinks to your page).