EFF Files Amicus Brief on Behalf of Tech Pioneers in Oracle v. Google Court Battle. Generally speaking, APIs are specifications that allow programs to communicate with each other. So when you type a letter in a word processor, and hit the print command, you are using an API that lets the word processor talk to the printer driver, even though they were written by different people. The brief explains that the freedom to re-implement and extend existing APIs has been the key to competition and progress in both hardware and software development. It made possible the emergence and success of many robust industries we now take for granted—for example, mainframes, PCs, and workstations/servers—by ensuring that competitors could challenge established players and advance the state of the art.