Application-based point of sale systems in mobile operating systems. A first application may generate a first URL directed to a second application, a parameter of the first URL comprising an identifier of the first application. A mobile operating system (OS) may access the first URL to open the second application. The second application may receive, from a server, a virtual account number (VAN). The second application may initiate a server on a port and generate a second URL directed to the first application, a parameter of the second URL comprising the port. The OS may access the second URL to open the first application. The first application may establish a connection with the server using the specified port and receive the VAN from the second application via the connection. The first application may autofill the VAN to a form field of a payment form in the first application.