Theories on Apple's W1 pairing

Since my last post, I’ve been putting a lot more thought into the pairing capabilities of Apple’s new W1 chip. A lot of folks are convinced the W1 itself is where the magic happens. I’m not saying that is impossible, but since Apple insists you must have the latest iOS/macOS and iCloud enabled for the seamless pairing to work, it should be obvious there is a lot more software involved than hardware.

If the W1 isn’t responsible for this pairing magic, what is? Without having a pair of W1 headphones I can only speculate, but after a lot of Bluetooth research I have some theories. For starters, if the hardware were responsible, yet allows non-Apple hardware to be paired, it seems unusual to go out of the way to build special functionality into an otherwise full Bluetooth stack. In theory, if the hardware could pair with more than 1-2 devices (something Bluetooth can already do), what would stop a non-Apple device from being the 3rd or 4th device to pair?

Some theories have been floating around that the W1 uses the new Bluetooth 5 specification. While this isn’t impossible or even that unlikely (except for it just being adopted a week ago), it only explains the better battery and reception of these devices. The specification doesn’t go into details about pairing, so regardless of Bluetooth 5, that doesn’t seem to be the culprit here.

It should be noted that Bluetooth has supported up to 8 device pairing for a while, but most hardware simply doesn’t support that. We could simply be seeing a pair of headphones that supports 8 “slots” for remembering devices, but that hasn’t been explicitly called out by Apple, nor should that require the latest iOS/macOS either. While this may be partly responsible, you would expect at least a little more delay or work to get other devices paired. From everything we’ve seen, the moment one device is paired, they all can see it.

My current running theory is that we’re seeing something similar or related to the Handoff functionality Apple has supported for a few generations now. I believe the real “magic” happens on the OS during pairing. The tricky part is that during pairing, unique information is passed around to encrypt and ensure the two devices are talking to each other. I believe this data is what is requiring iCloud, and somehow they are either “spoofing” with a fake identifier or injecting data on each device, then using Handoff as the means to identify which device has the “Bluetooth baton” so to speak. As we already know, you have to select which device uses the headphones manually, and this process does seem to have a slight delay. This could be Handoff making sure the old device “disconnects” and the new one “connects” in a way that the headphones seamlessly believe is effectively the same device.

This is all just theory, I haven’t touched an actual W1 set of headphones yet to put any of this to the test, but most of my theory revolves around the need for the latest OS and iCloud to do this pairing. If this were using any form of standard Bluetooth, there’s really no reason the OS should matter, as it doesn’t on other headphones that can be paired with multiple devices.

Why would Apple make such a big deal out of the W1 then? Marketing mostly. People don’t (usually) buy Apple products to understand the tech, but rather the exact opposite. They want something that “just works” and by branding anything with the W1 as offering this “seamless pairing” you ensure a good user experience. I’m not faulting them for making it seem like the W1 is doing all of the heavy lifting, I’m mostly just curious if my theories are correct :)


Aaron Dippner

Software engineer who loves to nerd out about technology, home automation, gadgets and everything else.

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