1. A system comprising: a merchant site server operated by a first entity; a payments portal service, hosted by one or more computing devices, in communication, via a network, with the merchant site server, wherein the payments portal service is operated by a second entity; and one or more non-transitory computer-readable media storing instructions that when executed by one or more hardware processors cause the system to: detect, by the merchant site server hosting a webpage of a merchant site, a request for the webpage for use in a payment transaction; determine, by the merchant site server, a storage location accessible to the merchant site server; generate, by the merchant site server, a request for a static widget, the request including the storage location and the static widget configured to provide a first functionality to perform at least part of the payment transaction, wherein the static widget comprises hypertext markup language code; send, by the merchant site server, the request to the payments portal service; receive, by the merchant site server, the static widget from the payments portal service, the static widget indicating the storage location; embed, by the merchant site server, at least one of first code or first scripts of the static widget into the webpage; provide, by the merchant site server, the webpage to a computer system in communication with the merchant site; determine, by the merchant site server, that an interaction is occurring with the static widget; collect, by the merchant site server, information associated with the interaction; store, by the merchant site server, the information in the storage location; access, by the merchant site server, the payments portal service to access a next iteration of the widget generated by the payments portal service, the next iteration of the widget generated based, at least in part, on the information associated with the interaction, the next iteration of the widget configured to provide a second functionality relating to the payment transaction; generate, by the merchant site server, a next iteration of the webpage containing the next iteration of the static widget by embedding at least one of second code or second scripts of the next iteration of the static widget into the webpage; and provide, by the merchant site server, the next iteration of the webpage to the computer system.