Apple iOS 27 adds a new iPhone Relay feature: two phones can share one eSIM number.

Apple has introduced a new iPhone Handoff feature in iOS 27, allowing two iPhones to switch back and forth and share the same phone number.

The feature briefly appeared on the feature list slide during the WWDC26 keynote, but Apple did not disclose details at the time. Overseas users demonstrated its actual functionality using the Xcode 27 device simulator.

The feature is configured in Settings > Cellular, where users designate one device as the primary and the other as the secondary.

The primary device retains the original eSIM, while the secondary device is assigned a companion eSIM, enabling number sharing.

All cellular-related settings are managed on the primary iPhone, and location sharing follows the device currently using the number.

However, enabling this feature requires certain prerequisites: both devices must be upgraded to iOS 27, and carrier network support is needed. Reports indicate that T-Mobile in the U.S. and Deutsche Telekom in Germany are expected to be among the first to support it.

After three months of beta testing, iOS 27 is expected to roll out officially this month.

Many believe it suits pairing a primary phone with a backup phone for travel, where the backup only retains basic calling functions to reduce the risk of loss or leakage. Some users also plan to use it with a future foldable iPhone.