Horizon is ready for iPhone Duo. You can buy a travel eSIM on the Duo itself, in Safari or in the Horizon app, with the phone folded or open, and install it on the same phone through the install link when your order offers one, so there is no QR code to scan. For a Christmas-market trip that crosses borders, choose the Europe eSIM; for markets in one country, a country plan can be enough. Validity does not start until your eSIM first connects to a supported mobile network at your destination.
This guide is for travelling with a new iPhone Duo for the first time: a phone just out of its box, a few days of Christmas markets, and a travel eSIM bought before you leave. It covers what Horizon has made ready for the Duo, which plan and how large an allowance to choose, and how to buy and install the eSIM on the Duo itself.
How Horizon is ready for iPhone Duo
The phone. The iPhone Duo is on Horizon's list of supported devices. It is eSIM-only worldwide, with no SIM tray, and it runs two eSIM lines at once, so your home number keeps one line and a Horizon data plan takes the other. Horizon plans are data-only, so the travel line sits beside your number instead of replacing it.
The app. Version 1.13 of the Horizon app, on the App Store since 31 October 2026, fits both of the Duo's screens, folded and open. On the open screen, the bar with your total and the payment button takes less room. When we checked version 1.12 on Apple's iPhone Duo simulator in October, folding or unfolding the phone did not restart the app: the layout followed the new screen.
The website. horizonesim.com is Horizon's store in Safari, with the same account and the same My eSIMs as the app. Its layout follows the width of the screen you are using, folded or open.
The install. On an iPhone, Horizon's install link, the Install with one tap button, opens the iPhone's own eSIM installer with everything pre-filled, and you confirm in Settings. It needs iOS 17.4 or later, and the Duo ships with iOS 27. That is what makes buying on the Duo itself simple: the install link puts the eSIM on the same phone, with no QR code to scan.
Before you pay: check the Europe list
Many Christmas-market trips cross borders: Munich to Salzburg, Vienna to Prague, or Vienna to Budapest by train. On 8 November 2026, the Europe plan listed Germany, Austria, Czechia, Hungary, Poland, France, Belgium and Denmark among its destinations, with one data allowance shared across them, so a train from Vienna to Prague needs no new plan at the border. The list, not the word Europe, decides where the plan works, so check every country on your route before you pay, including the ones you only cross by train. For markets in one country, compare that country's plan in country eSIMs.
For dated week prices on a route through Germany, Austria, Czechia and Hungary, read our Christmas-market eSIM comparison. For the markets themselves, our guides give the 2026 dates for Colmar, Brussels and Copenhagen.
Choosing the allowance
On a market day, the folded phone is easy to use with one hand while the other holds a hot drink: the map to the next square, the train time back to the hotel, a photo of a stall. Open and held sideways, the 7.6-inch inner screen can show two apps side by side, such as the market map next to the train timetable.
Maps, tickets and messages use far less data than video. If you film the lights and send the clips home, or stream on the big screen in the evening, choose a larger allowance or, if you bought with an account, keep an eye on the data left in My eSIMs. Hotspot sharing is free on every Horizon plan. Horizon fixed-data plans have no throttling.
Buy and install on the Duo, step by step
- Choose the plan. Open the Europe eSIM for markets in several countries, or a country plan for one, in the Horizon app or in Safari, folded or open.
- Pick the data and the days, then pay. If you buy with an account, your eSIM then appears in My eSIMs, in the app and on the website. If you buy as a guest with only your email, open it from the secure order link in that email.
- Install it at home over Wi-Fi. On the order page or in My eSIMs, tap Install with one tap and confirm in Settings. If iOS asks whether you will use the new eSIM at home or while you travel, this one is for travel. If your order offers no install link, open the QR code on another device's screen, or use manual entry with the SM-DP+ address and activation code from your installation details. Our help page explains both.
- Leave the line off until you arrive. Installing the eSIM does not start its validity. Keep the new line switched off until you land.
When you land, turn the Horizon line on, choose it for Cellular Data and turn on Data Roaming for the Horizon line only. Menu names vary by language and region. Keep data roaming off on your home line. Your home carrier may still charge for calls, texts or data on its own line. The installation guide has every step.
Keep the eSIM installed when you get home. If you bought with an account and My eSIMs shows Top up for the same destination, the new plan is added to the eSIM already on your phone, so there is no new QR code to scan. Some destinations need a separate new eSIM. eSIM top-ups explains the options.
Short answers
Is Horizon ready for iPhone Duo? Yes. The iPhone Duo is on Horizon's supported devices list, the Horizon app fits both of its screens, folded and open, and you can buy from the website in Safari on either screen.
Can I buy an eSIM for iPhone Duo on the Duo itself? Yes. Buy in the Horizon app or in Safari, then install it on the same phone with the install link when your order offers one, so there is no QR code to scan.
How do I install an eSIM on iPhone Duo without a QR code? Tap Install with one tap on the order page or in My eSIMs, then confirm in Settings. It needs iOS 17.4 or later. Without a link, use manual entry with the SM-DP+ address and activation code from your installation details.
Which plan covers Christmas markets in several countries? The Europe plan, if every country on your route is on its list. For markets in one country, a country plan can be enough.
When does my plan start? Installing the eSIM does not start its validity. Validity does not start until your eSIM first connects to a supported mobile network at your destination.
Horizon offers 24/7 human support in all languages, with guaranteed instant replies. Contact our team.
Sources
Checked on 8 November 2026: the Horizon app on the App Store and its version 1.13 notes; from Apple, the iPhone Duo technical specifications, the iPhone Duo overview and Use eSIM while traveling internationally with your iPhone; and Horizon's own plan pages.