An eSIM (Embedded SIM) is a rewritable SIM built into a smartphone or tablet. Unlike a conventional physical SIM card, it lets you write a carrier's information (a profile) to the device online, with no card to swap. The mechanism is based on an international standard drawn up by the GSMA (GSM Association). Support varies by model: some handsets take both a physical SIM and an eSIM, while others are eSIM-only. Apple, for example, states in its official specification sheet that the iPhone 16 and iPhone 16 Plus sold in the United States are eSIM-only and not compatible with physical SIM cards (as of August 2026). To find out whether your own handset is supported, check the manufacturer's specification sheet or your provider's list of compatible devices.
The appeal of eSIM is immediacy and flexibility. You can activate a line online without visiting a shop, completing the process by scanning a QR code or working through a dedicated app. On a handset that can hold several eSIM profiles at once, you can run it as a dual SIM device, keeping work and personal numbers on one phone, or add a local eSIM plan before travelling abroad to avoid steep roaming charges. From a design standpoint, it also lets manufacturers do away with the SIM tray opening.
Choosing between eSIM and a physical SIM depends on how you use your phone. An eSIM is better for fast activation and juggling multiple lines, but moving a profile off a handset that has broken down is not as simple as pulling out a card. A physical SIM is easy to move between handsets, with the straightforward appeal of being able to buy a local SIM at the airport and use it right away. One pitfall: if you delete a profile from the handset, reusing the same line may require the provider to reissue it. Check your provider's instructions for transferring a line before you reset a handset or trade it in.
When switching to an eSIM via MNP, some providers ask you to register the EID (the eSIM's identification number). You can find the EID under the device information in your handset's settings, though where it appears varies by model and OS version. MVNOs (budget SIM providers) and online-only brands also offer eSIMs in some cases, and both availability and the sign-up steps differ from provider to provider. Before signing up, it is worth confirming that your handset appears on the provider's list of compatible models. Review the switching steps in the number portability guide.