Google Merchant Center has added a new attribute named checkout_link_template. Including this new attribute lets you include a checkout URL in your product data which gives online shoppers the option to go directly to your checkout page from your free listings.
This seems related to what we reported about in June around Google Merchant Center new checkout buttons?
Emmanuel Flossie spotted this and explained "The quick checkout button is available only on free listings as of writing. Initially, it was called Quick Checkout. However, testing today, it seems Buy Now is used." He shared this screenshot:
Google wrote, "The checkout link template [checkout_link_template] attribute lets you include a checkout URL in your product data which gives online shoppers the option to go directly to your checkout page from your free listings. The standard “visit site” option will still remain on your free listings for shoppers that may want to learn more about your product."
You can learn more over here.
Forum discussion at Twitter.