Your save data only follows you if it is attached to an account, not to the phone. Link your progress to a Google Play Games, Game Center, publisher or email login before you switch, then sign in on the new device. This guide covers binding, transfer codes, and what to do when moving between Android and iOS.
Progress in most mobile games lives on the publisher server, but only if it is tied to a login. Before you touch the new phone, open the game, find the account or profile menu, and link your save to a store account, publisher ID or email address. Guest accounts are the number one reason players lose everything: they are attached to the device, not to you, and once the old phone is wiped there is often no way to recover them.
Many games offer a one-time transfer code instead of a normal login. On the old phone you generate the code in settings, then on the new phone you install the game, choose transfer or restore, and enter the code together with the password it gave you. These codes usually expire within a few days and can only be used once, so finish the move in one sitting. Screenshot the code and your player ID before you reset or sell the old device.
Moving within the same platform is usually seamless, but crossing from Android to iPhone can be blocked, because purchases and sometimes save data are tied to the store you bought them from. Check the official FAQ before assuming it works. Where cross-platform transfer is unsupported you may keep the account but lose paid currency. Instant browser games sidestep the issue completely: they open from the same URL on any device, so there is nothing to migrate at all.
What happens if I never linked my game account?
An unlinked guest save lives only on the old phone. If the device is reset, lost or the app data is cleared, the progress is usually gone for good — support can rarely restore it without a linked ID.
Do I need the old phone to transfer?
Only if you use a transfer code, since it is generated on the old device. If your progress is bound to an email or store account, you can simply sign in on the new phone.