WhatsApp when switching phones: chats, number and verification
Your WhatsApp chats depend on a backup you choose to make, your account depends on the number that receives the verification SMS, and if you turned on the security PIN, also on remembering it. Three different things, three different ways to get locked out.
In short: on the same system (Android to Android, iPhone to iPhone), WhatsApp moves your chats with a backup; across different systems, WhatsApp has its own official transfer tool. What never transfers on its own is the two-step verification PIN: if you forget it, there's a wait.
What happens
WhatsApp keeps your chats in a backup: on Google Drive if you use Android, on iCloud if you use an iPhone. Setting up WhatsApp on a new phone with the same system offers to restore that backup. The problem shows up when jumping systems: an iCloud backup can't be read by Android, and a Google Drive backup can't be read by iPhone.
For that jump, WhatsApp has long had its own tool: from an iPhone you can move your chats directly to an Android by following the relevant option in the app's settings, and the other way around, an Android can move its chats to a new iPhone using Apple's "Move to iOS" app. Both cases need the two phones nearby, connected to the same network, and — when moving to an iPhone — the iPhone needs to be freshly set up. Neither the call history nor the profile name transfers between different systems.
What doesn't change from system to system is how WhatsApp confirms it's really you: an SMS or call to your number, and if you turned on WhatsApp's two-step verification (a six-digit PIN, different from your email's 2FA), it will ask for that too.
Why it happens
Because the chat backup lives in each manufacturer's cloud (Apple or Google), not in a WhatsApp-owned cloud accessible from any system. And because your WhatsApp account is tied to your phone number, not to a username and password: whoever has that number and passes verification gets in. That same reason explains why WhatsApp pushes so hard for the two-step PIN: without it, controlling your number for a moment would be enough to control your account too.
Who it hits hardest
People who switch from iPhone to Android or back without knowing WhatsApp has its own transfer tool (and assume years of chats are lost, when they can actually be moved). And people who turned on the two-step PIN a while back, have forgotten it, and never set a recovery email: for them, every reinstall of WhatsApp on a new phone is a small scare.
It also hits people who share the same number between a personal and a work phone, or who reactivate an old SIM card: WhatsApp only keeps the account active on one device per number at a time, so installing it on the new phone closes the session on the old one, with or without your explicit permission.
What to check before you switch
- Do you know if your chats are in a recent iCloud or Google Drive backup?
- Are you switching systems (iPhone↔Android), and do you know you need the transfer tool, not the regular backup?
- Do you remember your WhatsApp two-step verification PIN?
- Do you have a recovery email set for that PIN?
- Are you keeping the same phone number on the new phone?
If it already happened to you
If you lost access to the number and can't receive the verification code, you'll need to recover the number with your carrier (a duplicate SIM or a new eSIM) before you can get back into WhatsApp: WhatsApp has no way to verify you without that number. If what you forgot is the two-step PIN and you have no recovery email, the app will ask for it again after a waiting period counted from your last connection; in the meantime, be suspicious of any message or website offering to "recover it" faster in exchange for a code.
Official sources: WhatsApp Blog: taking your chats with you · WhatsApp Help Center: two-step verification