A codec is the compression the audio goes through before it leaves your phone
Bluetooth does not have enough bandwidth to carry a CD-quality stream untouched.
So the phone compresses the audio, sends it across, and the headphones rebuild it.
The codec is the agreement about how that squeezing and rebuilding is done.
Every headphone spec sheet lists a few. Almost none explain what picking one costs you.
The four names you will actually see
| Codec | Peak bitrate | Where it comes from | Who can use it |
|---|---|---|---|
| SBC | ~328 kbps | Required in every Bluetooth device | Everything, always |
| AAC | ~256 kbps | Apple's preferred path | iPhone, iPad, Mac; patchy on Android |
| aptX / aptX HD | 352 / 576 kbps | Qualcomm | Many Android phones; never iPhone |
| LDAC | 330โ990 kbps | Sony, now in Android itself | Most modern Android; never iPhone |
SBC is the floor. It is mandatory, which is why any pair of headphones works with any phone.
Its reputation is worse than it deserves, because early implementations ran it at conservative settings.
AAC is the same family of compression used by the iTunes Store and Apple Music.
On an iPhone it is tightly tuned and sounds clean. On Android its performance has historically depended on which phone you bought.
aptX was designed to feel closer to wired, and its low-latency variants matter more for video sync than for music.
LDAC is the high-bitrate option, capable of roughly three times SBC's ceiling.
The codec you get is decided by whichever end of the link supports less, and that end is usually the phone.
Both ends have to agree, so the weaker device wins
This is the part that catches people out.
A codec is only used when the phone and the headphones both support it.
Buy LDAC headphones, pair them to an iPhone, and you are listening over AAC. There is no setting that changes it.
The same applies in reverse. An Android phone paired to AAC-only earbuds negotiates AAC or SBC, and the aptX badge on the box means nothing.
When negotiation fails, the connection falls back to SBC rather than dropping.
That fallback is silent. Nothing on screen tells you what you ended up with, unless you dig into Android's developer options.
A peak bitrate is a ceiling, not a promise
LDAC's 990 kbps figure describes ideal conditions.
In practice the link adapts. Walk into a crowded train car or a kitchen with the microwave running, and it steps down to 660 or 330 kbps to stay connected.
Many Android phones ship with LDAC set to adaptive by default, so the headline number is the exception rather than the rule.
Forcing the highest setting trades stability for numbers, and dropouts are far more audible than compression is.
Calls are a separate system entirely.
The moment a call connects, the phone switches to a voice profile at a fraction of the music bandwidth.
That is why good headphones can sound worse on a call than a $20 speakerphone does on music.
None of these codecs apply over a cable, either. Plugging in bypasses the whole question.
Fit and tuning move the sound more than the codec does
For most listeners on most tracks, the gap between AAC and LDAC is smaller than the gap between two pairs of headphones.
Seal, driver tuning, and how aggressively the noise cancelling reshapes the low end all change what you hear more than compression does.
Codec is a reasonable tiebreaker between two otherwise equal models. It is a poor reason to pick a worse-sounding pair.
The exception is a listener with a large lossless library, an Android phone, and quiet surroundings โ that combination can genuinely use the extra headroom.
Sony's flagship is the usual test case. The Sony WH-1000XM5 Review: 5 Numbers That Explain Why It Still Sells in 2026 covers where LDAC pays off.
Read the official LE Audio overviewBluetooth Special Interest Group โ
