Moving to a new Android phone does not affect the photos already on your Ultimate Backup — they stay exactly where they are. What changes is what the app on the new phone knows, and on Android that is worth knowing before the first backup runs.
Before you switch
While you still have the old phone, run one more backup and let it finish — How do I know if all my files were backed up? shows what a finished backup looks like. Check whether contacts backup is switched on while you are there: on Android it starts off, and only what was backed up can be restored later.
When it has finished, eject the drive before unplugging it — on Samsung phones through the My Files app, on other phones through Settings › Storage.
One button to leave alone around a switch: Erase All Files erases the drive's backup folder for that phone, and a new phone of the same model shares that folder, so it can clear both.
Setting up the app on the new phone
Install the app and sign in with the same account you used before rather than creating a new one — Which email address is my account under? can help if you are not sure which that was. Choose your product when asked.
On a Xiaomi, Poco, Oppo, Realme or OnePlus phone, turn on OTG before connecting the drive, or it will not be detected at all: Why isn't my drive detected on my Xiaomi, Poco, Oppo, Realme, or OnePlus phone?
Then open the Drive Picker and choose the top level of the drive, allow photos and videos with Allow all rather than picking individual items, and turn contacts backup back on if you want it — it starts off on a new phone. App Setup for Android has the screenshots, and Got a new phone? covers which drives fit which port.
What the first backup does
The drive keeps each Android phone's backups in a folder named after its model — "Galaxy S26", for example — not after a name you chose or the account you signed in with.
A new Android phone starts over. Restoring the phone from Google or Google One does not bring the app's record of what it has already backed up, so the first backup copies your photos and videos again. The quickest way to see where you stand is the big button on the Home screen: Start Backup means the app has no record yet and will copy everything, while Resume Backup means it found one. Start Backup or Resume Backup: what's the difference? explains the difference.
Where those files land depends on the model. A different model gets a folder of its own, which means a second full copy of your library on the drive, so check there is room for it. The same model writes into the existing folder, where a file of the same name is written over rather than doubled. A phone newer than the app's list of models gets a folder named with its model code — something like "SM-S948U" — until an app update teaches the app its proper name, at which point its backups continue in a second folder.
Does a second drive start where the first one stopped? covers the same ground for a new drive. If some of your photos live only in Google Photos rather than on the phone itself, see Backup Your Google Photos.
Getting your photos and contacts onto the new phone
Open Settings, then Restore Files. The list holds every device that has backed up to this drive, so your old Android phone is there — and so is any iPhone you have backed up, whose HEIC photos and MOV videos restore onto Android without trouble.
Restored files are placed in a folder called UB Restore, inside Pictures, Movies, Music or Download depending on the file type, and the app does not back them up again afterwards. Copy Files from Ultimate Backup to Android has the full steps.
For contacts, select them in the same list and tap IMPORT — your phone's own Contacts app finishes the job. Restore Contacts from Your Drive covers that on its own.
Coming from an iPhone
An iPhone's folder restores in exactly the same way, contacts included. The drive plugs into the new phone's USB-C port.
KeepSafe
KeepSafe follows your account, so signing in with the same email address is usually all it takes, and it switches itself back on afterwards. If your subscription does not appear, use RESTORE PURCHASE; billing stays with Google Play either way. KeepSafe Overview covers the rest.
Restore your contacts before KeepSafe runs for the first time on the new phone — each upload replaces KeepSafe's stored copy of your contacts with whatever is on the phone at that moment.
If you need any additional assistance, please contact Ultimate Backup support.