Critic reviews are available across mobile, tablet and desktop, allowing publishers to increase the visibility of their reviews and expose their reviews to new audiences, whenever a local Knowledge Graph card is surfaced. English reviews for businesses in the US are already supported and we’ll very soon support many other languages and countries.
Publishers with critic reviews for local entities can get up and running by selecting snippets of reviews from their sites and annotating them and the associated business with schema.org markup. This process, detailed in our critic reviews markup instructions, allows publishers to communicate to Google which snippet they prefer, what URL is associated with the review and other metadata about the local business that allows us to ensure that we’re showing the right review for the right entity.
Google can understand a variety of markup formats, including the JSON-LD data format, which makes it easier than ever to incorporate structured data about reviews into webpages! Publishers can get started here. And as always, if you have any questions, please visit our webmaster forums.