1. A method of dynamically performing data transformations on information that is transmitted between a user device and a web service, the method comprising: during a first communication session: receiving interface code from the web service; receiving one or more inputs from the user device, wherein the one or more inputs identifies: a data type that is associated with the interface code, and a data transformation to be applied to data instances matching the data type; and causing a definition file to be stored, wherein the definition file comprises: the data type, an indication of the data transformation, and a resource locator that is associated with the web service; during a second communication session: intercepting a transmission between the user device and the web service, wherein the transmission comprises: a data instance, and the resource locator; accessing the definition file using the resource locator; determining that the data instance matches the data type; causing the data transformation to be performed on the data instance to generate transformed data based on the determination that the data instance matches the data type; and inserting the transformed data into the transmission based on the determination that the data instance matches the data type.