Minimalistic, single-header library for decoding MP3. minimp3 is designed to be small, fast (with SSE and NEON support), and accurate (ISO conformant). Further information can be found in the oringal readme.
I have extended the project, so that it can be used as Arduino library. The result however is not very convincing: The decoder is too slow (e.g. on an ESP32) to decode any audio with a rate >= 32000 samples per second and the audio quality is quite poor.
You can download the library as zip and call include Library -> zip library. Or you can git clone this project into the Arduino libraries folder e.g. with
cd ~/Documents/Arduino/libraries
git clone pschatzmann/arduino-minimp3.git
I recommend to use git because you can easily update to the latest version just by executing the git pull command in the project folder.
I recommend to use this library together with my Arduino Audio Tools. This is just one of many codecs that I have collected so far: Further details can be found in the Encoding and Decoding Wiki of the Audio Tools.