The "Google December 2021 Product Reviews Update" looks at product review content. It does not penalize bad reviews but it promotes "insightful analysis and original research". Although this is a global launch, the algorithm only looks at English-language content with this first release.

It's not clear what percentage of searches will be impacted by this update. Google also said that they will refresh this new algorithm regularly without announcing the changes.

Google published best practices for online reviews. If you want your review to be found in Google's search results, do the following:

• Evaluate the product from a user's perspective.
• Demonstrate that you are knowledgeable about the products reviewed – show you are an expert.
• Provide evidence such visuals, audio, or other links of your own experience with the product, to support your expertise and reinforce the authenticity of your review.
• Share quantitative measurements about how a product measures up in various categories of performance.
• Explain what sets a product apart from its competitors.
• Cover comparable products to consider, or explain which products might be best for certain uses or circumstances.
• Discuss the benefits and drawbacks of a particular product, based on your own original research.
• Describe how a product has evolved from previous models or releases to provide improvements, address issues, or otherwise help users in making a purchase decision.
• Identify key decision-making factors for the product's category and how the product performs in those areas (for example, a car review might determine that fuel economy, safety, and handling are key decision-making factors and rate performance in those areas).
• Describe key choices in how a product has been designed and their effect on the users beyond what the manufacturer says.
• Include links to other useful resources (your own or from other sites) to help a reader make a decision.
• Consider including links to multiple sellers to give the reader the option to purchase from their merchant of choice.

Google recommends to focus on the quality and originality of the review, not the length.

"In this episode of AskGooglebot, John Mueller covers what type of redirect to use and how long a site should keep a redirect after a site move. [...]  To be certain that a redirect has been seen a few times,
we recommend keeping the redirect in place for at least one year."

"You need something from a specific store. Where is the location closest to your home? Are they open? Is your product in stock? Using Microsoft Bing or searching on Bing Maps, you will get rich results that will answer all these questions."

"Google is rolling out new layouts for the top stories section of the Google Search results. This includes not just the box carousel at the top but also double deckers, large image story with smaller image stories, and more variations. "

"Humans make the algorithms, so there's certainly a connection. But no, a random Google employee doesn't pick & choose which URLs get indexed. There's a lot of content on the web, it wouldn't be feasible to do that manually."