An image forming apparatus includes a communication interface, a processor, and a memory. The communication interface communicates with an external service including an authorization code flow. The memory stores a front-end application having a UI and a back-end application having no UI and registered in the external service, which are programs executed by the processor. The processor causes the external service to execute the authorization code flow based on the information of the back-end application in response to a request from the front-end application, receives an authorization code from the external service, causes the front-end application to redirect using a URL previously associated with the back-end application on the external service, and acquires an access token from the external service by the back-end application using the authorization code.