Short answer
Almost every app on your phone works abroad over eSIM data, because apps only need an internet connection. WhatsApp, Google Maps, airline apps, hotel apps, DigiLocker and your bank's app all run as they do at home. UPI at shop counters is the one that depends on the country, so check that before you fly.
You are standing at the Delhi T3 departure gate and wondering what will still work once you land in another country. Your boarding pass is in the airline app. Your hotel booking is in Gmail. Your family expects a WhatsApp message when you arrive.
This guide goes app by app. It tells you what each one does abroad, how much data it uses and what to set up at home first.
How apps work on a travel eSIM
An eSIM is a SIM built into your phone, so there is no small plastic card to swap. People often search for it as an "eSIM card", but nothing physical arrives. You get a QR code (see what an eSIM QR code is), scan it, and a data plan appears on your phone.
Apps do not care whether data comes from a SIM in Pune or an eSIM in Prague. They ask the phone for internet, and the phone supplies it. That is why your apps, logins and chat history stay exactly as they are.
Olysim's travel eSIM plans are data plans. See the full range of plans to match one to your country and number of days.
App-by-app: what you get and what it costs in data
The data figures below are rough averages. Your own use will vary with video quality and screen time.
| App | What you get abroad | Rough data use | Set up at home |
|---|---|---|---|
| Messages, photos, voice and video calls to India | About 0.5 MB a minute for voice, 5 MB or more for video | Turn on chat backup to Google Drive or iCloud | |
| Google Maps | Live directions, transit times, restaurant reviews | About 5 MB for an hour of navigation | Download an offline map of your city on hotel or home Wi-Fi |
| Airline apps (IndiGo, Air India, Vistara-merged Air India) | Boarding pass, gate changes, web check-in for the return flight | Under 5 MB a session | Save the boarding pass to your phone wallet |
| Bank apps (HDFC, SBI YONO, ICICI iMobile) | Balance checks, card controls, transaction alerts | A few MB a session | Switch on international card use inside the app |
| DigiLocker | A cloud copy of your documents | Small, a few MB per file | Upload passport and visa scans as a backup |
| Google Translate | Camera translation of menus and signs | Light for text, more for camera mode | Download the language pack |
WhatsApp: the app you will use most
WhatsApp calls and messages travel as data, so your family chats, group threads and photos carry on from wherever you are. A 20-minute video call home uses roughly 100 MB. A voice call of the same length uses about 10 MB.
Photos are the quiet data eater. WhatsApp compresses them, but a day of sending 30 holiday pictures can still add up to 50 to 100 MB. Switch off auto-download for media in WhatsApp settings so incoming group forwards do not pull data in the background.
Google Maps: download first, then navigate
Live navigation is light, around 5 MB an hour. The better habit is to download the offline map of your destination city on Wi-Fi at home. Tap your profile picture, choose Offline maps, then Select your own map.
Offline maps keep your saved hotel pin, station and sights on screen, and live traffic and transit timings still arrive over your eSIM. For ride apps like Uber and local taxi apps, read our guide on Google Maps, Uber and ride apps abroad.
UPI abroad: the one to check before you fly
UPI is the Indian payment system behind Google Pay, PhonePe and Paytm. It works at shop counters only in countries where NPCI International, the body that runs UPI overseas, has signed up local partners. That list includes the UAE, Singapore, Nepal, Bhutan, Mauritius, Sri Lanka and France, and it keeps growing.
Look at the current list on the NPCI International website before you leave. Then open your payment app and switch on its international payments option, which sits in the app's settings. The app also needs internet at the counter, and that is where your eSIM data does its job.
For countries outside the list, plan to pay with a forex card or an international debit or credit card. Your bank app, running over eSIM data, lets you set spending limits and freeze the card in seconds if you lose it.
Carry one payment method that works in your destination for certain, usually a card, and treat UPI as the bonus where it is supported.
Airline, hotel and document apps
Airlines push gate changes through their apps, often before the screens at the terminal update. Having data on at your connecting airport means you see the new gate while you are still at the food court. If a layover is part of your trip, read using an eSIM for just a layover.
Hotel booking emails and confirmation numbers sit in Gmail and in apps like MakeMyTrip and Booking.com. At a hotel front desk abroad, pulling up the booking on your phone takes seconds. Add a scan of your passport and visa to DigiLocker too, so a spare copy is one tap away.
Apps that behave differently in another country
Some apps open fine but show a different version of themselves. Streaming apps like JioHotstar and Netflix change their libraries by country, so a film you watch in India may be replaced by another title. Swiggy and Zomato list Indian restaurants for Indian addresses, so use a local option instead, such as Careem in the UAE or Grab in Southeast Asia.
Streaming is also heavy on data. An hour of video can use 500 MB to 1 GB, so save downloads on hotel Wi-Fi and keep your eSIM for maps, chats and bookings.
How much data these apps need in a day
Here is a realistic day of sightseeing: 2 hours of Maps navigation, 30 minutes of WhatsApp video calls, 30 photos sent, and a few bookings and bank checks. That comes to about 300 to 500 MB. Over a week, that is around 2 to 3.5 GB.
If you also share data with a travelling partner, add more. Our post on sharing eSIM data through hotspot explains how.
One week before you fly
✓ Update WhatsApp, Google Maps, your airline app and your bank app.
✓ Download the offline map for each city on your route.
✓ Switch on international use for your cards and your UPI app.
✓ Upload passport, visa and insurance scans to DigiLocker.
✓ Check that your phone supports eSIM on our compatible device list.
✓ Follow the install guide and set up the eSIM before you reach the airport.
If your phone does not support eSIM
Olysim also offers a physical SIM for phones without eSIM support. You pop it into the SIM tray, and the same apps run over its data in the same way. Check the device list above to see which option fits your handset.
The plain summary
Your usual apps carry on abroad with a travel eSIM. WhatsApp keeps you in touch, Google Maps gets you around, and your airline and bank apps stay in your pocket. UPI is the app to verify for your destination, and a card covers every other country.
