iPhone Handoff launches with iOS 27 — but only T-Mobile users get it on day one

Apple's iPhone Handoff arrives with iOS 27 on September 14, but almost nobody outside T-Mobile in the US and Deutsche Telekom in Germany will be able to use it at launch. The feature lets a single phone number work across two iPhones, switching automatically when you unlock either device. If you're on Verizon, AT&T;, EE, O2, Vodafone, or Three, you're waiting.

The feature

iPhone Handoff lets you run one number on two iPhones tied to the same Apple account. The primary device keeps its eSIM; the second iPhone gets a companion eSIM provisioned by your carrier. Unlock either phone and the number switches over — the screen shows "Switched to This iPhone" to confirm. Only one device holds the active line at a time, so there's no risk of calls ringing on both.

Setup requires both handsets to run iOS 27 or later, be connected to Wi-Fi, and have FaceTime, iMessage, and Messages in iCloud turned on. Some carrier features — call forwarding, caller ID, account management — stay pinned to the primary iPhone only. Apple Watch won't auto-switch between the two devices either.

Two-SIM configurations work if both eSIMs belong to supported carriers, in which case both lines switch together.

The catch

This is not a software-only feature. It depends on a new companion-eSIM backend architecture — distinct from standard eSIM provisioning — that carriers have to build out separately. T-Mobile and Deutsche Telekom are the only two confirmed launch partners, and independent sources note their backend infrastructure hasn't been confirmed as fully operational ahead of day one, meaning day-one delays are possible even for those subscribers.

Verizon and EE are expected to gain support by the end of 2026, per Android Authority. That's the only firm secondary timeline on the table. O2, Vodafone, and Three have made no announcements. Apple has not published a full carrier partner list, according to Gadget Hacks.

T-Mobile hasn't announced pricing. Carriers may charge a setup or activation fee — nothing has been ruled out.

What to do now

If you're on T-Mobile and own two iPhones capable of running iOS 27, you can try setting it up on September 14. Everyone else should bookmark this for Q4 2026 at the earliest — and even then, only if your carrier makes an announcement. Having an eSIM-capable phone does not mean your network is Handoff-ready.