Stripe announces a new, redesigned Checkout experience

You may have used the legacy version of Checkout to create a token or source on the client, and passed it to your server to create a customer and a subscription. If you are selling products where the amount or line items are determined dynamically (say, with a large product catalog or for donations), consider using the new version of Checkout’s server integration. You may have used the legacy version of Checkout to create a token or source on the client, and passed it to your server to create a customer and subscription.

Source: stripe.com