Facebook Pay is already in use across Facebook apps and services. However, this is now being extended beyond the Facebook platform.
From August, US businesses who are using participating platforms will be able to enable Facebook Pay as a payment option directly on their website. This will make checkout smoother for users, as they won’t need to re-enter payment information.
Initially this feature is being rolled out to Shopify Merchants. However, Facebook expects to expand availability to more platforms over time.