Payleven, the Square equivalent for the world outside of the US, has launched an API to complement its mobile payment device. Prior to the API, use of Payleven's mobile payment device required downloading the Payleven app (similar to Square's current model). However, the API allows developers to integrate Payleven's functionality within third party apps.
Square now has an E-commerce API that brings Square services to third party websites. Square is usually associated with its mobile credit card reader and complementary software. With the E-commerce API, merchants can use their own systems with all the benefit of Square's modern payment services.