Google upgraded the Rich Result Test now to support the validation of structured data for paywalled content. This means you can check live sites, any site, to see if they are implementing the paywalled content structured data properly and if Google Search understands that URL has paywalled content or not.
Google also added a section for generative AI to paywalled structured data.
Google wrote on X, "Starting today, the Rich Results Test supports validation of structured data for paywalled content. The tool can be found here: https://search.google.com/test/rich-results."
As an FYI, Google launched paywalled structured data in 2017 replacing first click free.
If you offer any subscription-based access to your website content, or if users must register for access to any content you want to be indexed, you can use paywalled structured data to communicate that to Google Search.
Here is what the tool shows for a FT.com URL:
I can see this being super helpful for a lot of you.
Forum discussion at X and WebmasterWorld.