The short answer
Install before departure only if the plan’s activation policy allows it. Keep the new line off until needed, then select it for mobile data on arrival and verify roaming instructions for that specific plan.
Treat installation and activation as two separate steps
Installing an eSIM downloads its profile to your phone. Activating a plan starts its service or validity according to a provider rule. Those events can happen together, but they do not always do so.
Before scanning the QR code, find the stated activation policy. If the plan begins on installation, preparing too early can use part of its validity. If it begins on the first supported network connection, advance installation may be possible.
The best time depends on the plan’s trigger
When advance installation is permitted, doing it on a stable private connection before departure gives you time to solve device or QR-code issues. Do not assume that airport Wi-Fi will be reliable enough for setup.
If installation itself starts the plan, wait until close to departure or arrival while following the provider’s deadline. Keep the confirmation and manual installation details available offline in case the QR code cannot be reopened.
Before departure: a safer setup checklist
Names vary between iOS and Android, but the preparation is similar. Avoid deleting an installed profile unless the provider explicitly tells you to do so; many QR codes are intended for one installation only.
- Confirm that the phone is unlocked and supports eSIM.
- Read the activation trigger, validity and installation deadline.
- Save the QR code and manual details somewhere accessible offline.
- Give each SIM line a clear label such as Home and Travel.
- Record which roaming and APN settings the offer requires.
On arrival: choose the correct data line
Enable the travel line, select it for mobile data and apply the roaming setting specified by the provider. Data roaming may need to be enabled for the travel eSIM because it can connect through a partner network; this does not mean enabling roaming on your primary line.
Turn off mobile-data switching if you do not want the phone to fall back to your usual SIM. Allow a few minutes for network registration, then check the selected line and restart the connection before changing advanced settings.
Common setup mistakes to avoid
Most preventable problems come from acting before reading the plan-specific instructions. Keep the provider’s wording available throughout setup.
- Scanning a one-time QR code on a different device.
- Starting a short-validity plan several days too early.
- Leaving the primary SIM selected for mobile data abroad.
- Deleting the eSIM because registration is not immediate.
- Changing APN details when the provider did not request it.