JS Morisset

Includes a 5 Star Rating in Schema markup:
<ol>
<li>If the Schema markup does not have an ‘aggregateRating’ property.</li>
<li>If Google allows an ‘aggregateRating’ property for that Schema type.</li>
</ol>
Google allows an ‘aggregateRating’ property for these Schema types and their sub-types:
<ul>
<li>Book</li>
<li>Course</li>
<li>Event</li>
<li>HowTo (includes Recipe)</li>
<li>LocalBusiness</li>
<li>Movie</li>
<li>Product</li>
<li>SoftwareApplication</li>
</ul>
If the Schema type in the Document SSO metabox is not one of these types (or one of their sub-types), then a 5 star rating cannot be added, as doing so would trigger an error in the Google search console. <a href="https://developers.google.com/search/docs/advanced/structured-data/review-snippet" rel="nofollow ugc">See Google’s Review snippet documentation for additional information.</a>

<h3>WPSSO Add Five Stars is a Fallback Solution</h3>
The Google’s Review Snippet technical guidelines reminds us to:
<blockquote>
<a href="https://developers.google.com/search/docs/advanced/structured-data/review-snippet#technical-guidelines" rel="nofollow ugc">Make sure the reviews and ratings you mark up are readily available to users from the marked-up page. It must be immediately obvious to users that the page has review content.</a>
</blockquote>
The WPSSO Add Five Stars add-on includes a 5 star rating if the document Schema markup does not already have an ‘aggregateRating’ property. It is always preferable to include actual ratings and reviews from your visitors and/or customers in the webpage. The WPSSO Add Five Stars add-on can be used in combination with any of the following third-party plugins and service APIs, or the <a href="https://wordpress.org/plugins/wpsso-ratings-and-reviews/" rel="ugc">WPSSO Ratings and Reviews</a> add-on.
Suggested Rating and Review Plugins and Services:
The <a href="https://wordpress.org/plugins/wpsso/" rel="ugc">WPSSO Core plugin</a> supports a selection of plugins that provide ratings and reviews:
<ul>
<li>WP-PostRatings</li>
<li>WP Product Review</li>
<li>Yotpo Social Reviews for WooCommerce</li>
<li>WooCommerce</li>
<li><a href="https://wordpress.org/plugins/wpsso-ratings-and-reviews/" rel="ugc">WPSSO Ratings and Reviews</a></li>
</ul>
The <a href="https://wpsso.com/" rel="nofollow ugc">WPSSO Core Premium plugin</a> also supports a selection of remote service APIs that provide ratings and reviews:
<ul>
<li>Judge.me (Ratings and Reviews)</li>
<li>Shopper Approved (Ratings and Reviews)</li>
<li>Stamped.io (Ratings and Reviews)</li>
</ul>
<h3>WPSSO Core Required</h3>
WPSSO Add Five Stars is an add-on for the <a href="https://wordpress.org/plugins/wpsso/" rel="ugc">WPSSO Core plugin</a>, which creates extensive and complete structured data to present your content at its best for social sites and search results – no matter how URLs are shared, reshared, messaged, posted, embedded, or crawled.

WPSSO Add Five Stars for Google Rich Snippets

Add a 5 star rating and review from the site organization if the Schema markup does not already have an 'aggregateRating' property.

M Asif Rahman

Tapan Kumer Das

If you review anything in your website, but you are not using Review Schema, you are just missing out. This plugin provide full support for Review Schema. Its free just give it a try and see the increase of Click Through Rate (CRT) massive improvement from Google Search.
<a href="https://wpdeveloper.net/free-plugin/wp-review-schema/" rel="nofollow ugc">PRO Version</a> is available with more Features, Premium support..
<blockquote>
Development on Github 
 This plugin is also <a href="https://github.com/ARCommunications/WP-Review-Schema" rel="nofollow ugc">available on github</a> and ready to take bugs and pull requests. For Support, you can buy the PRO version, this will give access to premium updates, support and features.
</blockquote>
<h4>What is a Rich Snippet?</h4>
It is basically a short summary of your page in the search results of Google, Yahoo, Bing and sometimes in the News feed of Facebook in nice format with star ratings, author photo, image, etc. 
<a href="http://www.seomoz.org/blog/schema-examples/" title="Rich Snippets Examples" rel="nofollow ugc">See Examples of Rich Snippets Here.</a>
<h4>How does a Rich Snippet help?</h4>
<ul>
<li>It gives search engines only the important & precise information to display in search result snippets.</li>
<li>Rich Snippets are very interactive (photos, star ratings, price, author, etc.) to let you stand out from competition</li>
<li><a href="http://dashburst.com/google-search-what-are-rich-snippets/" title="See the difference" rel="nofollow ugc">See what difference it makes</a> in CTR (Click Through Rate)</li>
<li>Helps you rank higher in search results</li>
<li>Helps Facebook display proper information when users share your links on Facebook.</li>
</ul>
**Supported Content Types: Review **
<h3>Donation</h3>
Buy the pro version if you want to support the development.
https://wpdeveloper.net/free-plugin/wp-review-schema/

WP Review Schema

The Ultimate Review Schema for WordPress. Improve your CTR & SEO Rankings. Add Review Schema And Look Good in Google.

WPSSO Add Five Stars for Google Rich Snippets vs WP Review Schema