Before You Upgrade Your Phone: What to Check First

The short answer

When you switch phones, work in this order: back up your data, check how two-step verification and authenticator apps carry over, and sort out your SIM or eSIM and payments. Erase the old phone last. Erasing cannot be undone, so do it only after confirming that everything you need is on the new phone. Screens and steps can differ by model and OS version, so following this order does not guarantee everything will go smoothly.

Back up first

On iPhone, Apple Support describes connecting to Wi-Fi, opening Settings, tapping your name, then going to iCloud, iCloud Backup, and Back Up Now. Stay connected to Wi-Fi until it finishes. You can move to a new iPhone with Quick Start, and Apple says to keep both devices plugged in and near each other until the transfer is complete. How long it takes depends on your network and how much data you have.

On Android, Android Help lists these preparations: charge both phones, make sure you can unlock the old phone, sign in to your Google Account, and back up your data. The same help page notes that photos, videos, and files may need to be moved by hand. Chat apps (such as LINE) each have their own transfer steps, so check each app's own guide.

Two-step verification and authenticator apps

Two-step verification means signing in with a code or similar check in addition to your password. This is where people most often get stuck when switching phones. If you use an authenticator app (an app that shows sign-in codes), how it carries over depends on the app and the service, so check the guidance from each provider.

For example, in a made-up case where you use an authenticator app for your work email and an accounting service, try signing in to both from the new phone before erasing the old one. Google Account Help describes backup codes you can use if you lose your phone or change your phone number. Each code works only once. For iPhone, Apple Support says to add a new trusted phone number if your number is changing.

SIM or eSIM, payments, and points

Apple Support advises asking your carrier about moving SIM or eSIM service. The process differs by company, so check the guidance from the carrier you have a contract with. Cashless payment and loyalty point apps also differ in how they carry over. List the apps you use and read each one's guidance ahead of time.

Erase the old phone last

Android Help says to confirm that all your data is on the new phone before resetting the old one. For iPhone, Apple Support lists steps such as unpairing an Apple Watch, signing out, going to General, then Transfer or Reset, then Erase All Content and Settings, and removing the old device from your list of trusted devices.

If it is still not solved

For moving data, check the relevant Apple Support or Android Help page. For your line, contact your carrier. For authenticator apps and app data, check the guidance from each app's provider. Screen names in the English interface may differ from the Japanese help pages cited here.