# eSIM

> A SIM card built into the phone, which you load by download instead of by hand.

- Level: Basic
- Topics: Networks
- URL: https://tidbit.legios.com.ar/esim/
- In Spanish: [eSIM](https://tidbit.legios.com.ar/es/esim/)

Every phone needs a **SIM** to join a mobile network: it holds the secret that proves to the carrier that this line is yours. For decades that was a small plastic card you pushed into a tray. An **eSIM** does the same job with a chip soldered inside the phone, and the line's details arrive as a downloadable profile.

To activate it, you scan a QR code the carrier gives you or follow the steps in its app. A single eSIM can store several profiles, so you can keep your local number and add a cheap data plan when you travel, without hunting for a shop at the airport. Many phones, tablets and smartwatches support it, and some recent iPhone models sold in the United States no longer have a tray at all.

Losing the physical card also removes a small risk: a thief cannot just pull it out and put it in another phone. The flip side is that moving to a new phone means transferring the profile through the phone's menus or asking the carrier, and that the same transfer process is a target for SIM swapping fraud if the carrier does not check who is asking.

## An analogy

A plastic SIM is a physical key you carry on a keyring. An eSIM is a door with a keypad: the code is sent to you, and you can store the codes for several doors in the same place.

## Keep in mind

- An eSIM is a SIM built into the device; the line arrives as a downloadable profile.
- It is usually activated by scanning a QR code or through the carrier's app.
- One device can store several profiles, handy for travel data plans.
- Changing phones means transferring the profile instead of moving a card.

## Go deeper

- [eSIM on Wikipedia](https://en.wikipedia.org/wiki/ESIM)
- [eSIM (GSMA, the mobile industry association)](https://www.gsma.com/solutions-and-impact/technologies/esim/)

## Related terms

- [SIM card](https://tidbit.legios.com.ar/sim-card/): The small chip card that tells the mobile network which line is yours.
- [Chip](https://tidbit.legios.com.ar/semiconductor-chip/): A sliver of silicon carrying billions of tiny switches that compute and remember.
- [QR code](https://tidbit.legios.com.ar/qr-code/): A square pattern of dots that a phone camera reads, usually to open a link.
- [Tablet](https://tidbit.legios.com.ar/tablet/): A computer that is just a big touchscreen, between a phone and a laptop.
- [Wearables](https://tidbit.legios.com.ar/wearables/): Small computers you wear on your body, like smartwatches, fitness bands and smart rings.
- [SIM swapping](https://tidbit.legios.com.ar/sim-swapping/): A scam where someone takes over your phone number to receive your security codes.