To transfer WhatsApp from your old phone to your new phone:
Android to Android: Backup WhatsApp data on the old phone, install WhatsApp on the new phone, and restore the backup.
iPhone to iPhone: Backup WhatsApp data on the old iPhone, install WhatsApp on the new iPhone, and restore the backup.
Android to iPhone: Use the “Move to iOS” app to transfer limited data, including WhatsApp account info, chats, media, and settings.
iPhone to Android: Use Samsung Smart Switch and a USB-C to Lightning cable to transfer WhatsApp chats and media.