Why did Apple put a Thread radio in its newest iPhones?

The latest iPhones will be the first Thread-enabled smartphones, according to Apple. The iPhone 15 Pro and iPhone 15 Pro Max (but not the iPhone 15) will support the open-source smart home protocol Thread to “open up future opportunities for Home app integrations,” the company announced during its iPhone 15 event in Cupertino.

How exactly this will impact Apple’s smart home isn’t immediately clear. The Verge asked around on the ground at the event, and it doesn’t seem like even Apple is sure what the Thread radio will do yet.

Thread is a mesh networking protocol designed specifically for low-powered, low-bandwidth smart home devices. It aims to reduce latency, help prolong battery life, and improve the reliability of connected devices— i.e., make your smart lights respond to a motion sensor as fast as if you flipped a regular old light switch.

It’s becoming a popular connectivity protocol for battery-powered smart home gadgets like sensors, shades, lights, and locks and is one of the main protocols for these devices in Matter.

One possible use for Thread in the iPhone is that it could be used as a Thread border router. Thread devices need a Thread border router to connect to the internet and other IP-based networks, allowing you to control them from outside the house and to connect to non-Thread devices. It could also help enable device-to-device connectivity in Apple Home.

Interestingly, details surfaced yesterday around the possibility that Google will allow Android phones to become Thread border routers. Mishaal Rahman spotted that Google is working on a Thread network stack for Android that could allow Android devices such as Pixel smartphones and tablets to be Thread border routers — as long as they already have a Thread radio in them (sorry, Pixel Tablet). Google didn’t immediately respond to a request for comment on its plans.

I don’t know of any Android phones with Thread radios in them, currently. But Google does have a big Pixel event coming up next month.

However, using a smartphone as a border router doesn’t seem like the best implementation. Thread border routers should be always-powered devices, according to The Thread Group, and most current Thread border routers are smart speakers or Wi-Fi routers. So, it’s possible there is some other future implementation here that will make the smart home more interoperable and easier to use. We can always hope!

Rahman speculates that the Android Thread news could also be tied to Android TV devices (newer Apple TV devices support Thread). I’ve reached out to The Thread Group for more details on how Thread-powered smartphones can fit into a Thread network.

Along with Wi-Fi and ethernet, Thread is the main protocol used by Matter, the new smart home standard that Apple helped found. Thread devices don’t need a central hub or bridge as an intermediary; something similar protocols such as Zigbee and Z-Wave do require. But a Thread network does need a Thread border router to connect to the internet and other networks.

You can have multiple Thread border routers in a Thread network, and they can support each other, so if one device drops offline (or leaves the house), your Thread devices will still work as expected. Thread border routers from different manufacturers should also work together, although that’s a feature that has run into some problems as the major players try to figure out how best to work with each other.

Apple has been a strong supporter of Thread since 2018, when it joined The Thread Group. (Apple’s Vividh Siddha has been its president since 2021). The company launched its first Thread-enabled product, the HomePod Mini, in 2020, then added support to the Apple TV 4K (second- and third-gen), followed by the second-generation HomePod earlier this year. Now, with the iPhone on board as a Thread device, my guess is we’ll see Thread come to the iPad next.