# eSIM

> A digital SIM built into your phone that lets you download a mobile plan over the internet instead of inserting a physical SIM card.

Source: https://viasimo.com/glossary/esim/
Also known as: embedded SIM, digital SIM, electronic SIM

---
An eSIM (embedded SIM) is a digital SIM card built directly into your phone, tablet or smartwatch. Instead of inserting a plastic chip, you download a mobile plan over the internet, which means you can get connected in a new country without visiting a shop or swapping anything physical.

The hardware itself is a small rewritable chip soldered inside the device. When you buy a plan, the operator sends an [eSIM profile](/glossary/esim-profile/): a data file containing the credentials your phone needs to register on a network. Most providers deliver it as a QR code; you scan it, wait a minute or two, and the new line appears in your settings alongside any existing SIM.

For travellers this solves the two classic pain points of getting online abroad: queuing at an airport SIM kiosk and losing access to your home number. Because most modern phones support [dual SIM](/glossary/dual-sim/), your physical SIM can stay active for calls and texts while a travel eSIM handles data. Our [complete guide to eSIMs](/magazine/what-is-an-esim-complete-guide/) explains the technology step by step, and [eSIM vs physical SIM](/magazine/esim-vs-physical-sim/) compares the two formats directly.

## Common confusions

The word eSIM is used for two different things: the chip inside the phone and the plan you download onto it. You cannot buy the chip; it either shipped with your device or it did not. Most phones released since 2018 include one, but support varies by model and region, so check [device compatibility](/device-compatibility/) before buying a plan. A carrier-locked phone is another frequent trip-up: the eSIM will install but refuse to connect until the lock is removed.

A concrete example: before flying to [Japan](/destinations/japan/), you buy a travel eSIM at home, scan the QR code over your own Wi-Fi and leave the line switched off. When you land, you toggle it on and enable data roaming for that line; you are online before you reach baggage claim, and your home number never left your phone.