How Do Apple AirTags Work? Ultra-Wideband Explained

(Image: Shutterstock)

Apple AirTags are $29 devices you place on an item—keys, wallet, backpack—and use to track them down should they be lost or stolen. But how does it work? It's all thanks to a technology called ultra-wideband (UWB).

UWB is not new. Its appearance in the AirTags is akin to the actor who has a breakthrough performance in time for the Oscars after working for decades in Hollywood. Known as "pulse radio" in the early 2000s, UWB was all about fast, wireless data transfers. It tried to compete with Wi-Fi, but largely ended up in some limited medical and military equipment.

The name "ultra-wideband" comes from the ability to transmit info across a wide radio bandwidth, from 500MHz to several gigahertz. That gives it a short range. Ultimately, it's a radio tech a lot like Wi-Fi and Bluetooth, but it doesn't use the 2.4GHz frequencies. That makes UWB compatible with other wireless technologies—there's no signal interference. It's also low power and provides data in real-time thanks to pulses sent every other nanosecond.

Spectral density for UWB and narrowband (Image: FiRa Consortium)

That is why UWB excels at the job it has today: Finding things. The days of trying to use it for data communication are over. Today's UWB can accurately pinpoint other devices, tell you if it's in motion, and lead you to it. UWB can, in theory, pinpoint things down to the centimeter. Walls and other obstacles are not much of an issue.

Other real-world possibilities for UWB include using it in smart locks for passive, keyless entry, which means the tech can tell not only if you're approaching, but also if you're inside or outside the building or car. It could even start the vehicle for you. It could power a new wave of garage door openers that don't require you to push a button. You could skip having a debit card when you approach an ATM, or carrying a credit card for payment since the robot in the drive-thru window will know you're waiting for your fries and a shake. Sharing and data transfers, AirDrop-style, will take on entirely new dimensions with better location awareness, something Samsung is already working on with its Nearby Share app. UWB could even help us all keep a decent social distance of six feet via warnings to our devices.

Wi-Fi and Bluetooth can try, but neither can determine a location with the exactitude of UWB.

Plus, UWB is locked down. It has security extensions built right into the specification (the PHY layer of IEEE 802.15.4z, to be precise), so it can do random number generation and cryptography. What does that mean to you? You probably don't need a VPN to secure your smart tracking tags, at the very least. That'll be important if it's unlocking your doors, as well as giving away your location.

This is mostly built on work being done by an industry group called the FiRa (fine ranging) Consortium. Ranging, in this case, means measuring. FiRa exists to grow the ecosystem of UWB products. Adoption by big-name companies in smartphones will do exactly that.

But there's also the Car Connectivity Consortium and the UWB Alliance, which formed in 2018, ahead of FiRa. They all may have competing UWB tech out there someday, which would be unfortunate, but hopefully they'll work together on different aspects of UWB.

UWB sensors were first built into the iPhone 11, plus Apple Watch Series 6, in 2019 as Apple prepared for the future, but not in all countries. Samsung started putting them in the Galaxy line with the Note 20, S21 Ultra 5G, and S21+, ready to work with its own SmartTag+. (The less expensive Galaxy SmartTag is Bluetooth-only.) China's Huawei is also reportedly looking into it. At this point, expect that every company, even car companies, are looking closely at UWB.

SmartTags (Image: Samsung)

Apple's application of the tech is uniquely Apple-centric, of course. UWB's range isn't that much better than that of Bluetooth, around 30 feet, but Apple's implementation means that if an AirTag is active around any Apple device with UWB built-in, the AirTag can still be tracked by the owner. (For more details, read our Apple AirTag review).

This is more relevant than ever, as new data indicates that more people want an item tracker than ever, now that Apple has made them appear legit. Sorry, Tile.

By the way, don't confuse any of this with the branding on Verizon 5G Ultra Wideband. The mobile carrier is not using any kind of UWB technology with 5G.

About Our Expert

Eric Griffith

Senior Editor, Features

My Experience

I've been writing about computers, the internet, and technology professionally since 1992, more than half of that time with PCMag. I arrived at the end of the print era of PC Magazine as a senior writer. I served for a time as managing editor of business coverage before settling back into the features team for the last decade and a half. I write features on all tech topics, plus I handle several special projects, including the Readers' Choice and Business Choice surveys and yearly coverage of the Best ISPs and Best Gaming ISPs, Best Products of the Year, and Best Brands (plus the Best Brands for Tech Support, Longevity, and Reliability).

I started in tech publishing right out of college, writing and editing stories about hardware and development tools. I migrated to software and hardware coverage for families, and I spent several years exclusively writing about the then-burgeoning technology called Wi-Fi. I was on the founding staff of several magazines, including Windows Sources, FamilyPC, and Access Internet Magazine. All of which are now defunct, and it's not my fault. I have freelanced for publications as diverse as Sony Style, Playboy.com, and Flux. I got my degree at Ithaca College in, of all things, television/radio. But I minored in writing so I'd have a future.

In my long-lost free time, I wrote some novels, a couple of which are not just on my hard drive: BETA TEST ("an unusually lighthearted apocalyptic tale," according to Publishers' Weekly) and a YA book called KALI: THE GHOSTING OF SEPULCHER BAY. Go get them on Kindle.

I work from my home in Ithaca, NY, and did it long before pandemics made it cool.

The Technology I Use

My first computer was a Laser 128, an Apple II-compatible clone with an integrated keyboard, matched with an eye-straining monochrome green monitor. I used it to type papers in college for other people for money...until I discovered the Mac SE in the college computer room. That changed my life. My first cellphone was a Samsung Uproar—the silver one with the built-in MP3 player from the Napster days (the pre-iPod era).

I use an iPhone 15 Pro hourly and an iPad Air infrequently (but I'm always in the market for a cheap Android tablet). I have a PlayStation 5 just to play Spider-Man, and several Windows machines, including a work-issued Lenovo ThinkPad. I talk to Alexa and Siri all day long. I do the majority of my computing on a 15-inch LG Gram laptop attached to a Thunderbolt hub to run a multi-monitor setup—I overdid it on the power needed to simply work from home.

I'm most at home in Microsoft Word after decades of writing there. More and more, I turn to services like Google Docs, using tools like Grammarly. I use Google's Chrome browser due to an addiction to several extensions I think I can't live without, but probably could. I use Excel extensively on data-intensive stories, but for chart creation, we've switched over entirely to using Infogram for interactive features that are hard to find elsewhere. I do a lot of graphics work for my stories, but limit myself to the free and amazing Paint.NET software to edit images.

I'm a firm evangelist for using the cloud for backup and syncing of files; I'm primarily using Dropbox, which has never failed me, but I also have redundant setups on Microsoft OneDrive, plus extra picture backups on Amazon Photos and iCloud. Why take chances? For entertainment, mine is a streaming-only household—my kid has never seen network TV and barely been exposed to commercials, thanks to Roku and Amazon Music. The house is peppered with smart speakers from Amazon for instant gratification and control of smart home devices like multiple Wyze cameras and Nest Protect smoke detectors. I've got accounts on all the major social networks, to my horror. I have a robot vacuum for each floor of the house. I want a 3D printer, but not sure what I'd use it for.

Read the latest from Eric Griffith

Read full bio