Abstract: A web server system identifies a webpage being accessed by a user through a client terminal. The webpage is among a set of possible webpages that are accessible through the client terminal. Different identifiers are assigned to different ones of the webpages. Responsive to the identifier of the webpage, a set of user interface (UI) input field constraints is selected that define what the webpage allows to be input by a user to a set of UI fields provided by the webpage. An output text string is obtained that is converted from a sampled audio steam by a speech-to-text conversion server and that is constrained to satisfy one of the UI field input constraints of the selected set. The output text string is provided to an application programming interface of the webpage that corresponds to one of the UI fields having user input constrained by the UI field input constraint of the selected set.