Modern applications commonly make use of several subsystems, usually a frontend and a backend. The communication link between these subsystems is commonly an API. Different APIs such as REST and SOAP have been around for a long time but with the increasing use of internet, other techniques as GraphQL have been developed to compensate for older techniques. The aim of this thesis is to measure the performance of GraphQL and how it compares to SOAP and REST and how the overhead reduction of GraphQL will affect the performance. The main method used to evaluate the performance differences between GraphQL, REST and SOAP is an experiment. The results show that GraphQL has the worst performance in all test cases. GraphQL has the lowest packet size out of all three APIs when only a few fields are fetched, however the packet size increases rapidly when multiple fields are requested.