An API is just a set of methods, properties etc which allow one program to communicate with another even tho they come from totally different people. So your question isn't quite correct. An API may consist of many things like Web Services, DLL libraries etc etc so what you need to ask yourself first is what do you need your API to do? Will it be accessed by others or just by me locally (on your machine and directly from your host too)? If it will only work locally than you can develop a binary file and use that. If you need it to be accessible from a public place you would develop either a Web Service or some kind of gateway to accept the POST/GET requests. Hope that gives you a little bit of clue on what to do next.