https://paypal.github.io/paypalnativecheckout-docs/

The Paypal Checkout Native SDK provides an in-context mobile experience by supporting a lightweight client-side integration, keeping your existing server-side integration intact. The SDK maintains feature parity with PayPal web checkout while offering a faster mobile-optimized experience. Include a native checkout experience that keeps the user inside your merchant application with some simple integration steps.

Getting Started

To get started please follow instructions on obtaining a Merchant ID here