What Is Dual SIM? — DSDS, DSDV, and DSDA Explained

Dual SIM lets you run two phone lines on a single device — each with its own number, carrier, and data plan. The key difference between modes is whether both lines stay active simultaneously, and what happens to one line when the other is in a call. Understanding the mode your device supports helps you choose the right setup.

The Four Dual SIM Modes

There are four distinct modes for dual SIM operation. Each defines how many SIMs can stay on standby, which network generations are supported, and whether both lines remain active during a call.

DSSS (Dual SIM Single Standby)

Only one SIM is active at a time. You can insert two SIMs, but you must manually switch which one is active. The inactive SIM cannot receive calls or texts while the other is in use. This mode is found only on older devices and is rarely encountered today.

DSDS (Dual SIM Dual Standby)

Both SIMs are on standby simultaneously, so you can receive calls and texts on either number without switching. However, when one SIM uses a 4G or 5G connection, the other SIM is pushed down to 3G. In regions where 3G has been shut down, this can mean the second SIM loses connectivity during active data use on the first.

DSDV (Dual SIM Dual VoLTE)

Both SIMs maintain 4G or 5G connections at the same time. Because both lines use VoLTE (Voice over LTE), calls are delivered over the data network rather than a 3G circuit — making DSDS’s 3G fallback unnecessary. This is the current mainstream mode on modern smartphones.

One limitation remains: during an active call on one SIM, data on the other SIM is paused. You cannot, for example, take a call on SIM A while streaming video over SIM B.

DSDA (Dual SIM Dual Active)

Two separate radio transceivers are used — one per SIM. Both SIMs remain fully active and independent at all times. You can take a call on SIM A while SIM B continues data transmission without interruption. This eliminates all the restrictions of DSDS and DSDV.

The tradeoff is higher battery consumption, since two transceivers draw power simultaneously. DSDA is found on select high-end Android devices.

Mode Comparison

Device Support

iPhone

iPhones support DSDS but do not support DSDA. Apple’s official documentation uses the term DSDS. Both SIMs can make and receive calls, send texts, and use data — though data on the second SIM pauses during an active call on the first.

• iPhone XS, XS Max, XR (2018) and later: physical SIM + eSIM dual SIM configuration
• iPhone 13 series and later (including iPhone SE 3rd gen): dual eSIM — two eSIM profiles active simultaneously
• US-sold iPhone 14 and later: eSIM-only (no physical SIM slot); dual eSIM only

In Settings > Cellular, you can assign each line to calls and data independently. The detailed setup walkthrough is covered in Dual SIM Setup (iPhone) (coming soon).

Google Pixel

• Pixel 3a and later: DSDS — physical SIM + eSIM
• Pixel 7 and Pixel 7 Pro (2022) and later: dual eSIM — the first Android devices to support two eSIMs simultaneously
• US-sold Pixel 10, 10 Pro, and 10 Pro XL: eSIM-only (Pixel 10 Pro Fold retains a physical SIM slot)

Dual eSIM on Pixel 7+ is implemented via MEP (Multiple Enabled Profiles), introduced in Android 13 and defined in GSMA SGP.22 v3.0.

Samsung Galaxy

Samsung Galaxy S20 and later flagship models support eSIM alongside physical SIM for dual SIM configurations. eSIM availability depends on the region and whether the device is carrier-locked. A carrier-locked Galaxy may not expose the eSIM option even if the hardware supports it.

Common Use Cases

Separate Work and Personal Numbers

Keep a work number and a personal number on one device. You can assign different ringtones to each line, route calls to the correct number, and avoid carrying two phones. You set which line handles calls and which handles data — each independently.

Reduce Data Costs Without Sacrificing Call Quality

Use your primary carrier for voice calls while routing all data through a lower-cost plan on the second SIM. This is a common setup in markets where MNOs (large carriers) charge a premium for data but offer reliable call quality, while MVNOs provide cheaper data on the same underlying network. Use SimFinder to compare available plans side by side.

Backup Line for Network Outages

Carrier networks experience outages. With a second SIM on a different network, your connectivity continues even if your primary carrier goes down. This is especially relevant for people who rely on mobile data for work or remote access.

Travel: Keep Your Home Number + Add Local Data

This is the most widely used travel configuration:

• Keep your home SIM active for calls and SMS
• Add a local travel eSIM for data at local rates (no international roaming charges)
• Your home number remains reachable for SMS two-factor authentication codes from banks and apps

Most travel eSIMs are data-only — they do not include a phone number or SMS capability. Voice calls over the travel eSIM are handled via VoIP apps such as WhatsApp or FaceTime. This is covered in detail in 4 Ways to Stay Connected Abroad.

Install the travel eSIM profile before departure while on a Wi-Fi connection, and it typically activates when your device first connects to a supported network at your destination.

Things to Know Before You Start

Explicitly Set Your Preferred Data SIM

In a dual SIM setup, the device needs to know which SIM to use for mobile data. If you do not configure this, the device may default to the more expensive line. On iPhone, go to Settings > Cellular > Cellular Data and select the SIM you want for data.

Calls Interrupt Data on the Other SIM (DSDV/DSDS)

On DSDV and DSDS devices, answering a call on SIM A pauses data on SIM B for the duration of the call. This affects background downloads, active VoIP calls, and streaming. If continuous data on both lines is a requirement — for example, running a video call through one SIM while the other handles incoming calls — you need a DSDA-capable device.

eSIM + Physical SIM Requires No Extra Slots

If your device has one physical SIM slot and eSIM support, you already have everything needed for a dual SIM configuration. The physical SIM handles one line; the eSIM handles the other. You do not need a dual-SIM hardware variant. For more on how eSIM works, see What Is eSIM?.

Carrier Lock Can Block eSIM Access

A device purchased through a carrier may be SIM-locked or have eSIM activation restricted to that carrier. Even if the hardware supports eSIM, the option may be hidden or disabled until the device is unlocked. Check your carrier’s unlock policy if you plan to add a second line from a different provider.

Summary

To compare plans for a dual SIM setup, use SimFinder to search by carrier, data, and price.