Recently a JSON-LD for SEO customer emailed me about their collections in Shopify:
I would like to check with you if this will create rich snippets for my collections?
So for example the brand "collection" - Acme? Will this show an accumulative total of reviews for each product within the collection, so that the search term "acme" will show with a star rating on google search?
That's a good question and something that seems like it would be valuable.
Who wouldn't want to be able to combine all of their product reviews for a brand and get that Rich Snippet in Google?
Seeing "113 reviews" on a page is much better than "1 review", "3 reviews"... across a few dozen pages.
Unfortunately that's not what Google wants their Rich Snippets used for.
Google's guidelines say they only want reviews on single products and not a collection of products.
Provide review and/or rating information about a specific item, not about a category or a list of items. For example, "hotels in Madrid," "summer dresses," or "cake recipes" are not specific items.
It's similar for marking up Products too:
Use markup for a specific product, not a category or list of products. For example, "shoes in our shop" is not a specific product.
That's why JSON-LD for SEO only adds the product and reviews structured data on the individual product pages and not on collection pages.
You really don't want to push too hard against such clear guidelines from Google or you risk losing your Rich Snippets and maybe more.
Install JSON-LD for SEO and let it handle all of this for you automatically. Easy-peasy.