If you're an iPhone user, consider buying a model with Apple's proprietary H2 (or older H1 or W1) chip. It makes Bluetooth pairing painless—there's no need to open the Settings menu because your phone automatically prompts you to connect whenever the headphones are nearby. The chip also improves connection stability and increases the wireless range. Currently, only Apple and Beats (which Apple owns) make headphones with this component. Everyone—iPhone and Android users—needs to pay attention to which Bluetooth codecs their headphones support. Codecs determine how your device compresses audio streams before sending them to your headphones (most Bluetooth implementations don't currently support lossless audio streaming). You need to make sure that your headphones and phone support the same high-end codecs if you want the best listening experience. Our guide to Bluetooth codecs details everything you are likely to encounter and our reviews note which ones each model supports.