MP3 (MPEG-1 Audio Layer III)

MPEG-1 Audio Layer III — the dominant lossy compression format for two decades and still the universal-compatibility baseline in 2026. Perceptual encoding throws away frequency content the encoder predicts will be psychoacoustically masked; bit rates from 32 kbps to 320 kbps are valid.

At 320 kbps CBR or VBR-V0 the audible delta from CD-quality is small-to-imperceptible on most material in most listening contexts. At 128 kbps the artifacts are obvious to anyone listening through decent equipment.

Universally supported. AAC and Opus are the modern-codec successors with better quality at equivalent bitrates.