mp3

MP3, short for MPEG-1 Audio Layer III (and later MPEG-2 Audio Layer III), is a lossy audio coding format designed to compress digital audio data for efficient storage and transmission. It was developed within the Moving Picture Experts Group as part of the MPEG-1 standard in the early 1990s, with subsequent extensions in MPEG-2. MP3 exploits perceptual coding: it uses a psychoacoustic model to remove audio components considered inaudible or less important, then uses predictive coding and other techniques to further reduce data size. The result is a compressed bitstream that preserves perceptual quality at lower bitrates.

MP3 encoding offers various bitrate settings, typically ranging from 32 to 320 kilobits per second. Common listening bitrates include 128 kbps and 192 kbps. MP3 supports stereo audio, with options such as joint stereo to improve efficiency. It supports constant bit rate (CBR) and variable bit rate (VBR) encoding. The format uses a frame-based structure; each frame contains a header and a block of audio data, which may include metadata like CRC and side information. Files typically use the .mp3 extension and often carry metadata in ID3 tags.

Historically, MP3 was instrumental in the mainstream adoption of digital music in the 1990s and 2000s, aided by widespread software players and hardware devices. While later formats such as AAC, Ogg Vorbis, and Opus offer improved efficiency, MP3 remains widely supported across platforms and devices. Licensing historically involved patents held by various entities, notably Fraunhofer IIS, but most MP3 patents have expired in many jurisdictions, reducing licensing constraints for implementations.