When iOS 27 lands later this month, it will include a feature called iPhone Handoff that Apple first mentioned in passing during the WWDC keynote in June. The company did not provide specifics at the time, but a new demo in Xcode 27’s Device Hub has now revealed how the feature is designed to work. In short, iPhone Handoff will let users pair two iPhones and share a single phone number across both devices. One handset will act as the primary device, while the other will be marked as a companion. Calls, texts, and other services linked to that number will be available on either device, depending on which one is active or within reach.

The feature arrives at a curious moment in Apple’s product cycle. Reports have long pointed to a foldable iPhone, sometimes called the iPhone Ultra, expected to launch in the near future. The name Ultra suggests a premium and likely expensive device. If the foldable iPhone is positioned as the ultimate iPhone for media, productivity, and multitasking, it may also be larger and heavier than a standard smartphone. For that reason, Apple appears to be offering an answer to a simple question: what happens when you want to use a regular phone but still need to stay connected to your primary number?

That answer, based on the Xcode demo, is a “companion” pairing. After connecting two iPhones, users can choose which device is their main iPhone. The other device can then act as a secondary endpoint for the same line. When the user chooses to switch, the companion can become the active handset for calls and messages. The demo is short, but it suggests the transition is designed to be nearly invisible. The feature is called Handoff, which fits with Apple’s existing naming convention for moving tasks between devices.

A closer look at the demo

The Xcode 27 Device Hub appears to show a new setup flow for Handoff. Users are presented with an option to pair an additional iPhone. The system then asks whether the new phone should be used as the main device or as a companion. If companion is selected, the phone receives a configuration profile or similar credential that ties it to the main device’s number. The demo does not show exactly how the underlying call routing works, nor does it indicate whether both phones can ring at the same time. The most likely scenario is that the user can manually switch or that the active device is the one with the strongest signal or most recent use.

The distinction is essential because there are several different ways a shared number could work. In one implementation, calls to the primary number would ring on both devices, and the user could answer either. Another implementation would allow the user to select which phone is active before leaving home, avoiding the need to manage incoming calls on two phones simultaneously. Apple’s wording, “seamlessly share one number,” suggests the first approach, but the companion language could support either. If two phones can share the same number, then the line is not strictly tied to one piece of hardware in the traditional carrier sense.

Why a companion iPhone now?

The timing of the feature is interesting. A foldable iPhone Ultra, if it arrives soon, could be a large device that some users won’t want to carry everywhere. The entire point of a phone is portability, and a foldable model may push the limits of what fits comfortably in a pocket or purse. By letting users pair their expensive new foldable with an older or less expensive iPhone, Apple makes it easier to leave the Ultra at home for a day at the beach, a concert, or a bike ride. Rather than turning off the primary line or swapping a SIM card, a user can simply grab the companion phone and walk out the door.

The cracked iPhone 13 is mentioned as an example. Many people hold onto an older iPhone after upgrading, using it as a backup device for travel or as a hand-me-down. If that backup iPhone can share the same number, it becomes far more useful. Instead of carrying both a primary and a separate backup phone, users can treat the older device as a lightweight companion that can be taken on errands or to environments where the newest hardware might be at risk. Those older devices are also a reasonable testing ground for a feature that Apple may eventually expand.

Carrier support and limitations

Not every carrier will support iPhone Handoff at launch. The code references T-Mobile US and Deutsche Telekom, which suggests the two carriers took part in early trials or will be among the first to offer the feature. Supporters beyond those providers are unknown. This is not a simple firmware update: sharing one phone number across two physical devices requires the carrier to route calls and messages in a new way. It also requires provisioning an additional eSIM profile or other network credentials. Carriers have long controlled how phone numbers are assigned to devices, and they have commercial reasons to be cautious about enabling services that could reduce the number of lines a customer pays for.

One reason T-Mobile and Deutsche Telekom are involved could be their history with early eSIM adoption. T-Mobile was one of the first carriers to support Apple Watch with a standalone number via eSIM, and Deutsche Telekom has been a forward-looking partner for Apple in Europe. T-Mobile US is also majority-owned by Deutsche Telekom, which may make it easier for Apple to work with a coordinated group across Europe and the United States. That relationship could also help with international roaming and cross-border usage, since a feature like iPhone Handoff is likely to be used by travelers who want to keep one number while using a second phone in another country.

Carrier support may also depend on whether a market has modern infrastructure. Sharing a number across two phones requires the network to recognize both devices as part of the same subscription. Older 2G and 3G networks were not designed for this kind of flexibility. The reference to T-Mobile US and Telekom.de suggests that 5G standalone and IP-based voice services are likely to be a prerequisite. Many carriers around the world are still in the middle of migrating to VoLTE or managing legacy networks, which could delay wider availability.

Continuity, Handoff, and the Apple ecosystem

Apple has had a feature called Handoff for years, letting users start an email on an iPhone and continue on a Mac or iPad. The company also allows Wi-Fi calling on other Apple devices when the iPhone is nearby. But iPhone Handoff appears to be different: it does not require the main iPhone to stay in the same location. If both phones can receive the same calls and texts, the companion must be able to connect through the carrier rather than relying on a local Bluetooth or Wi-Fi connection to the primary phone.

The concept is not entirely new. Apple Watch with a cellular connection supports numbers that follow the iPhone, but the watch is not an independent phone with a full keyboard. Android manufacturers have offered similar features for years. Samsung, for example, has experimented with “Call & Text on Other Devices” for Galaxy phones and tablets. What makes iPhone Handoff interesting is that Apple has built it into the operating system and tied it to a system-level setting, rather than leaving it to carriers or device makers to piece together.

The underlying technology likely depends on IP Multimedia Subsystem (IMS), which powers VoLTE and Wi-Fi calling. If the primary number is registered to a network-based identity rather than to a single SIM, then multiple devices can be signed in to that identity simultaneously. This is similar to how Apple can deliver iMessage to an iPad because the message is tied to an Apple ID, not to the phone number. With iPhone Handoff, the phone number itself becomes a cloud-like identity, while carriers handle the actual voice and SMS delivery.

Privacy, security, and pairing

Adding a second device to a phone number presents security challenges. If someone gains physical access to a companion phone, they could receive calls and messages intended for the user. Apple will presumably require the same kind of authentication used for setting up an Apple Watch or adding a new device to an Apple ID. The demo in Xcode suggests the pairing happens in the Settings app and is tied to the iCloud account. It may also use the same end-to-end encryption that protects iMessage and FaceTime, so a companion cannot intercept anything it was not intended to see.

Users will likely be able to choose which phone is the “main” device after pairing. This could be accomplished by selecting a handset in Settings or using an automatic rule based on which device was used most recently. For the companion to be useful, it should be able to act independently. That means the feature may require two active eSIM profiles, each with its own unique identifiers, despite sharing the same phone number in the carrier’s network database. Another approach would be to use a secondary eSIM that is valid only when

Source: The Verge News