dualSIM

DualSIM refers to the capability of a mobile device to host two separate subscriber identity modules (SIMs) at the same time, allowing connections to two different mobile networks. The feature can support two active numbers for calls, texts, and data, or a combination where one SIM handles voice while the other provides data, depending on device settings and carrier support.

Configurations commonly include two physical SIM cards in two slots, or one physical SIM plus an embedded SIM (eSIM). Some devices support two eSIMs. Network behavior is described by terms such as DSDS (dual SIM dual standby), where both SIMs are available but only one may be used for data at a time, and DSDA (dual SIM dual active), where both SIMs can be active concurrently for calls and data. In practice, many devices prioritize data on one SIM while the other is used for calls or standby, with automatic switching based on signal and user preferences.

Use cases include international travel without roaming, by using a local SIM alongside a home line; separating personal and business lines on a single device; and improving coverage by selecting the strongest network available.

Limitations and considerations include compatibility with local bands and carrier policies, potential limitations on simultaneous data usage, battery impact, and varying availability of eSIM support by region and model. Security considerations apply to both slots, including standard SIM-related risks such as SIM swapping.

Many modern smartphones support dual SIM, with models from Apple, Samsung, and other manufacturers offering one physical SIM and one eSIM or two physical slots, reflecting broad market adoption.