What Is an eSIM? How It Works in the UK, Keeping Your Number and Travel

An eSIM is a SIM built into your phone. Instead of a plastic card, your network sends the plan to the phone, usually through a QR code or its app. It works like a physical SIM for calls, texts and data, and you can keep your number when you move to one.

How an eSIM works

1. Check your phone supports eSIM: its mobile or SIM settings show the option to add one.
2. Choose a plan from a network that offers eSIM on that plan.
3. Scan the QR code or follow the network’s app, over Wi-Fi.
4. The plan is active once the phone shows the network’s signal.

Keeping your number

Moving to an eSIM does not mean a new number. To move your number to another network, text PAC to 65075 from your current phone and give the code to the new network; the move usually completes within one working day. If you do not want to keep the number, text STAC to 75075 instead.

eSIM and physical SIM

• Setting up. An eSIM can be added in minutes without waiting for a card in the post; a physical SIM needs the card.
• Changing phone. A physical SIM moves by hand. An eSIM is transferred in the phone’s settings or reissued by the network.
• Two numbers. Many phones hold a physical SIM and an eSIM, or two eSIMs, so work and personal numbers can live on one phone.
• Support. Some older phones take a physical SIM only; some recent phones take eSIM only.

eSIM when you travel

A travel eSIM adds data for another country alongside your UK plan, so your UK number stays on for calls and texts. Check your UK plan’s own roaming terms first: some include roaming in certain countries, others charge by the day.

Before you switch to eSIM

• Confirm the phone supports eSIM, and that the plan you want offers it.
• Keep Wi-Fi available while you set it up.
• When you change phone, move the eSIM before resetting the old one.
• The price depends on the plan, not on whether it is an eSIM.

New to the UK

A SIM-only plan on an eSIM can get a UK number working quickly after you arrive, alongside your number from home. Getting a phone contract when you are new to the UK explains which plans depend on UK credit history.

How Wisemium helps

Wisemium shows SIM-only plans from the providers it works with, not every plan on the market, and names each provider before you leave. Once you have a plan, add it to Wisemium and the price, the data allowance and the date the contract ends are kept on record. Wisemium does not sell mobile plans itself.