In the streaming era, music is accessed from a variety of online services, ephemeral in nature and never living on board the device. However, the online audio revolution really kicked off with the development of one very special format. The subject of bitter raps and groundbreaking lawsuits, this development from Germany transformed the music industry as we know it. Twenty-five years on from the date the famous “.mp3” filename was chosen, we take a look back at how it came to be, and why it took over the world.