TL;DR
- An eSIM is a programmable chip soldered into a device; you download operator profiles onto it rather than swapping a physical card, allowing a single device to hold and switch between multiple carrier profiles.
- Adding a foreign or travel eSIM profile typically takes a few minutes via a QR code scan or app download, either before departure or on arrival if you have a data connection.
- Your phone must be eSIM-capable and, critically, must be network-unlocked - a locked handset will refuse to activate a profile from a different operator family.
- Travel eSIM providers (who operate as MVNOs reselling local network capacity) often offer data-only plans; voice and SMS may route over VoIP or be unavailable.
- Switching between your UK home profile and the travel profile can be done in device Settings without needing to physically handle any SIM hardware.
What Makes eSIM Different from a Physical SIM
A physical SIM card is a removable chip whose identity - the IMSI number that identifies your subscription to a network - is encoded at manufacture. Swapping a physical SIM is a hardware action: you take out one card and insert another. An eSIM (embedded SIM) is a chip permanently soldered to the device's motherboard, but it is reprogrammable. Instead of swapping hardware, you download an operator "profile" - a software representation of a subscription - onto the eSIM. The profile contains the same cryptographic credentials that a physical SIM would carry, and the network treats it identically.
The GSMA, the international industry body that governs mobile standards, defines the technical specification for eSIM under its Remote SIM Provisioning (RSP) standards. Consumer devices use the M2M or Consumer RSP architecture, with profile downloads managed by a Subscription Manager Discovery Service. In practice, this means the process of adding a carrier profile is reduced to scanning a QR code, tapping a link in an app, or, on some platforms, entering an activation code manually - all of which can be completed in minutes.
Device Compatibility and the Lock Status Question
eSIM support has become widespread in flagship and mid-range smartphones since approximately 2018, when major manufacturers began integrating the chip. However, not every handset is eSIM-capable, and even among capable devices, the number of simultaneous profiles that can be stored varies by model. Some devices can store up to eight profiles but activate only one or two at a time; others permit only a single active profile.
The lock status of the handset is equally critical. A phone sold by a UK operator on a subsidised contract may be network-locked, meaning it will only activate profiles from that operator's group. Attempting to download and activate a travel eSIM profile from an unrelated carrier on a locked handset will fail at the activation step. UK operators are legally obliged under Ofcom rules to unlock handsets at the customer's request once the minimum lock period has passed (typically after the contract minimum term or upon full device payment). Unlocking is usually processed online or by contacting customer services. Confirming that the handset is unlocked before travelling is an essential pre-departure step if you intend to use a travel eSIM.
| Step | Action | When to Do It | Notes |
|---|---|---|---|
| 1. Check compatibility | Confirm device supports eSIM; check Settings > About or manufacturer spec | Before booking travel eSIM | Not all devices list eSIM explicitly; look for "Add Mobile Plan" option |
| 2. Unlock handset | Request network unlock from UK operator if required | Several days before travel | Ofcom rules require operators to unlock on request; processing time varies |
| 3. Purchase travel eSIM plan | Buy a data plan from an MVNO offering coverage in destination country | Before departure or on arrival via Wi-Fi | Plans are typically data-only; check if voice/SMS included |
| 4. Download eSIM profile | Scan QR code or use provider's app to install profile onto eSIM chip | Before departure (recommended) | Requires internet connection at download time; use home Wi-Fi or cellular |
| 5. Activate at destination | Switch active SIM to travel profile in Settings > Mobile / Cellular | On arrival | UK profile remains stored; switch back at any time |
Cost Savings Versus Standard Roaming
UK operators that include EU roaming at no additional cost - as required under voluntary commitments that most major operators have maintained post-Brexit - make the cost case for a travel eSIM less compelling within the European Economic Area for many customers. However, for destinations outside the EEA, for longer trips where the roaming data allowance is insufficient, or for travel to regions where operator roaming agreements produce high per-MB or per-day charges, a travel eSIM can offer meaningful savings.
The saving mechanism is straightforward: instead of routing traffic through your UK operator's roaming agreement (which involves wholesale inter-operator charges), a local eSIM profile connects you directly to a local network at domestic or MVNO wholesale rates. Because travel eSIM providers typically aggregate capacity across many destination networks and sell it at a competitive price, the effective cost per gigabyte can be significantly lower than a UK operator's out-of-bundle roaming rate. The trade-off is that your UK phone number is not reachable on the travel SIM; calls and SMS to your UK number go to voicemail unless you forward them or use a VoIP number.
Switching Between Profiles
On both iOS and Android, switching the active profile is handled entirely in software without touching the physical phone. On iOS, the relevant menu is Settings > Mobile Service; on Android the path varies by manufacturer but is typically Settings > Network & Internet > SIMs or Settings > Connections > SIM Manager. Both platforms allow you to label profiles (for example "UK - Home" and "France - Travel") and select the default for calls, data, and SMS independently.
Many travellers configure their device so that the travel eSIM handles data, while the UK physical SIM (or UK eSIM profile) handles voice calls - useful if you need to remain reachable on your UK number. Dual-SIM devices (which may combine a physical SIM slot with an eSIM, or have two eSIM slots) allow both profiles to remain registered to their respective networks simultaneously, meaning you can receive UK calls on your home number while data traffic routes over the travel profile. This simultaneous standby configuration does increase battery consumption slightly compared to single-SIM use.
What this means in practice
James, a project manager from Leeds, travels to Japan for two weeks on business. His handset is eSIM-capable and he requested an unlock from his UK operator a week before departure. Before leaving home, he purchased a Japan-specific data plan from a travel MVNO, downloaded the eSIM profile over his home broadband, and labelled it "Japan Travel" in his phone settings. On landing at Narita, he switched his active data SIM to the Japan profile; his UK physical SIM remained registered for voice so his UK clients could still call him. Over fourteen days of navigation, video calls, and cloud file access, his data costs on the travel eSIM were a small fraction of what his UK operator's out-of-bundle Japan roaming rate would have charged for the same volume. On returning to Heathrow, he switched back to his UK profile in seconds.
Related Guides
How we verified this
This article draws on GSMA Remote SIM Provisioning specifications (SGP.02 and SGP.22), Ofcom guidance on SIM unlocking obligations for UK operators, and publicly available device manufacturer documentation for iOS and Android eSIM management. Roaming regulatory context references the European Electronic Communications Code and post-Brexit UK operator roaming commitments as reported by Ofcom.
Disclaimer: Kaeltripton.com is an independent UK editorial publisher. We are not regulated by Ofcom or the FCA and we do not sell or arrange mobile services, insurance, or financial products. This content is for general information only and is not legal, financial, or technical advice. Rules, prices, and operator policies change. Verify the current position with Ofcom, GOV.UK, the ICO, or your provider before acting. ICO registered ZC135439. Last reviewed: 2026-06-05.
Frequently Asked Questions
How do I use an eSIM abroad?
To use an eSIM abroad, you need an eSIM-capable device, a network-unlocked handset, and a purchased travel eSIM plan. Download the operator profile (usually via a QR code or app) before or during travel while on a Wi-Fi connection. Once installed, switch the active data line to the travel profile in your device settings. Your original UK profile remains stored and can be reactivated at any time without physical SIM changes.
Can I add a foreign eSIM to my phone?
Yes, provided your device supports eSIM (most flagship smartphones released after 2018 do) and is network-unlocked. A locked handset will reject profiles from operators outside its permitted group. Once the device is unlocked - which UK operators must facilitate on request - you can download profiles from any compatible carrier worldwide. The number of profiles a device can store simultaneously varies; check your device specification for the limit.
Do I need to unlock my phone to use a travel eSIM?
In almost all cases, yes. A network lock prevents the device from activating SIM profiles from operators outside the locking carrier's group. Ofcom rules require UK operators to unlock handsets at the customer's request, typically once the minimum contract term has been completed or the device has been paid for in full. Unlocking is usually processed online or through customer services and may take up to a few working days, so request it before travel.
How do I switch between eSIM profiles?
Switching between eSIM profiles is done entirely in software. On iOS, go to Settings > Mobile Service and select the profile you want to activate. On Android, the path is typically Settings > Network & Internet > SIMs or a similarly named SIM management menu. You can label profiles for easy identification and set different defaults for calls, data, and SMS. No physical SIM handling is required; the switch takes effect immediately or within seconds.
Is an eSIM profile the same as a physical SIM?
Functionally, an eSIM profile contains the same credentials - IMSI, authentication keys, and network configuration - that a physical SIM card carries. The network cannot distinguish between the two and authenticates the subscription identically. The difference is purely in the hardware: a physical SIM is a removable card with credentials written at the factory, while an eSIM profile is downloaded software written to a permanently embedded chip. Both represent a mobile subscription and can hold a phone number.
