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Connections & formats

AAC

Also called Advanced Audio Coding, AAC codec

AAC, Advanced Audio Coding, is the lossy compression format used by Apple Music and iTunes downloads, and the preferred Bluetooth codec on iPhones. At 256 kbps most listeners cannot tell it from lossless in blind tests.

05001,0001,500kbpsSBC328AAC256aptX352aptX Adaptive280–420aptX HD576LDAC330 / 660 / 990aptX Lossless~1,100FLAC (CD)~700–1,000CD PCM1,411
AAC over Bluetooth runs at about 256 kbps, the rate at which most listeners cannot tell AAC from lossless in blind tests. aptX reaches 352 kbps, LDAC up to 990 and uncompressed CD-quality PCM 1,411.

AAC was designed as the successor to MP3 and does more with the same bits. As a file format it is the standard for Apple’s ecosystem, and YouTube uses it alongside Opus; as a Bluetooth codec it is what an iPhone uses with almost any headphone, since Apple does not license aptX or LDAC.

Bluetooth AAC quality depends on the encoder in the phone: Apple’s is good, and some Android implementations are poorer, which is why Android users often prefer other codecs. Any Bluetooth AAC stream is re-encoded from the source, so playing an AAC file over AAC Bluetooth compresses it twice. Streaming services that advertise Lossless use FLAC or ALAC instead.

Related terms