> ## Documentation Index
> Fetch the complete documentation index at: https://support.onroamly.com/llms.txt
> Use this file to discover all available pages before exploring further.

# What is an eSIM?

> A SIM built into your phone. You download a plan to it instead of inserting a card, and it runs alongside your normal SIM.

An eSIM is a SIM card that's already inside your phone. Instead of a plastic card you push into a tray, it's a small chip on the phone's board, and you download a mobile plan onto it. It does exactly what a normal SIM does; you just skip the card.

## Why it's good for travel

* **No shop, no queue.** You buy the plan online and install it in a minute, anywhere you have internet.
* **Buy before you fly.** Install at home, land connected.
* **Keep your normal SIM in.** Nearly every eSIM phone is dual-SIM: your normal number stays active for calls and texts while the eSIM handles data abroad.
* **More than one at a time.** Phones can store several eSIMs, so you can keep a Japan plan and a Europe plan on the same phone and switch between them.

## Physical SIM vs eSIM

|                 | Physical SIM           | eSIM                        |
| --------------- | ---------------------- | --------------------------- |
| Where it lives  | A card in the tray     | A chip built into the phone |
| Getting one     | Buy a card, swap it in | Download a plan             |
| Switching plans | Swap cards             | Tap between profiles        |
| Losing it       | Easy to lose or damage | Nothing to lose             |

## Do I need to take my normal SIM out?

No. Leave it in. The only settings that matter are which SIM your phone uses for data and whether roaming is on for your normal SIM (it should be off). The install guides cover both.

## Does my phone have one?

Most phones sold since 2018 do, but a few don't, and a phone locked to a carrier can't use another provider's eSIM. See [Does my phone support eSIM?](/getting-started/does-my-phone-support-esim)