MP3s were all the rage even before you got that giant, clunky, gen-1 iPod, but today, MP3s are officially a thing of the past.
Major developer Fraunhofer IIS held most licenses for the use of MP3s, and it has announced it is terminating those licenses in light of better, lower-bit files, such as AAC, and the industry shift toward those files. The company's official announcement can be read online, and reads as follows:
On April 23, 2017, Technicolor's mp3 licensing program for certain mp3 related patents and software of Technicolor and Fraunhofer IIS has been terminated.
We thank all of our licensees for their great support in making mp3 the defacto audio codec in the world, during the past two decades.
The development of mp3 started in the late 80s at Fraunhofer IIS, based on previous development results at the University Erlangen-Nuremberg. Although there are more efficient audio codecs with advanced features available today, mp3 is still very popular amongst consumers. However, most state-of-the-art media services such as streaming or TV and radio broadcasting use modern ISO-MPEG codecs such as the AAC family or in the future MPEG-H. Those can deliver more features and a higher audio quality at much lower bitrates compared to mp3.