Abstract: In accordance with an embodiment, described herein is a system and method for providing on-demand localization in a microservice application environment. Generally described, an on-demand localization environment enables the system to serve localized user interface labels for an existing, e.g., monolith application, on-demand - without impacting the existing setup of the application or its present means of handling localizations. The described approach can ensure that only the localization which is needed for a particular user interface or visited page is served, without incurring additional round-trips back to the server for user interface messages that could have been served from the client. For applications and user interfaces comprising more than one module, the system can retrieve the localization for each of the modules in a single call.