1. A computer-implemented method, comprising: invoking a user input interface on a mobile device; invoking an optical input extension of the user input interface; capturing optical input via one or more optical sensors of the mobile device; determining textual information from the captured optical input; based on analyzing the optical input, wherein the analyzing comprises: determining a restricted optical character recognition (OCR) alphabet based on the optical input; and performing OCR using the restricted OCR alphabet; identifying desired textual information among the determined textual information based on the OCR; selectively providing the desired textual information to the user input interface without relying on feedback from the user; and wherein the user input interface is invoked in response to detecting a user interaction with a user interface element configured to receive textual information.