APIs have long been a staple of the programming world. If you want to use a library, you need to understand its API. If you want someone to use your library, then you need to provide (and document) an API. In the modern programming world, APIs extend not only to libraries, but also to Web frameworks and (increasingly) Web APIs — which allow software to communicate across computers, networks, and languages. But what are the best practices in creating APIs? n this talk, Kevin Lack (now at Facebook, but then the CTO of Parse), describes the elements of a great API. No matter what language you’re using, you can likely learn something about how to improve your APIs from this talk.