A method for mediating messages between at least two browser extensions using a web browser of a computing device includes receiving a request from a first browser extension via a messaging application programming interface provided by the web browser, wherein a receiver of the request is a second browser extension determined by the messaging application programming interface based on a requested functionality included in the request from the first browser extension. The method includes sending, using the messaging application programming interface, the request to the second browser extension when the requested functionality is available in the second browser extension, and sending an error message to the first browser extension using the messaging application programming interface when the requested functionality is not available.