A new phone can bring across almost everything from the old one the first time you switch it on. The catch is that it only offers to do this once, and anyone who clicks past it has extra work on their hands.
Before you put the old phone away
Get this ready while you still have both phones in front of you:
- The password to your Google account (Android) or Apple ID (iPhone). Without it you will get nowhere.
- The old phone charged to at least half and connected to Wi-Fi.
- About an hour of time. Transferring a full phone takes a while.
Android to Android
The first time you switch the new phone on, an option appears called Copy apps & data. That is the one you want. You then join the phones with the cable that usually comes in the box, or wirelessly by confirming a code.
Practically everything comes across: contacts, photos, messages, apps and their settings, the wallpaper and the icon layout. You will usually have to sign in to the apps again.
iPhone to iPhone
Put the new phone next to the old one. The old one offers Quick Start by itself and shows a blue pattern that you scan with the new phone. The rest runs on its own.
If the offer does not appear, you can restore from an iCloud backup instead. That does require the backup to exist — so it is worth running one manually on the old phone first: Settings → your name → iCloud → iCloud Backup → Back Up Now.
Android to iPhone and the other way round
It works, but less smoothly. Going from Android to iPhone there is an app called Move to iOS that you install on the old phone. In the other direction, Google offers a transfer by cable or through your account.
In both cases, expect paid apps not to come across — you bought them in a different store. And messages tend to be the most troublesome part.
If the new phone is already set up
No disaster, just more work. Contacts and photos can be pulled in through your Google or iCloud account, and apps you reinstall by hand. Alternatively you can reset the phone to factory settings and go through setup again — which makes the transfer offer appear once more.
Do not rush to get rid of the old one
Keep the old phone for at least a month. Almost always something turns out not to have come across — usually messages from some app, or two-factor authentication tied to that particular handset. Before you pass it on, wipe it with a factory reset and take out the SIM and any memory card.
I am happy to help with the transfer, often remotely. The best time to get in touch is before you switch the new phone on for the first time.