Install WhatsApp on the new phone
Open WhatsApp and verify the same phone number
Allow WhatsApp to access contacts, photos, and files
When prompted, tap Restore from backup
Sign in to the same Google account on Android or the same Apple ID on iPhone
Make sure the backup exists on Google Drive or iCloud
Keep the phone connected to Wi-Fi during restore
Wait for chats to restore
Wait for media to finish downloading
Open WhatsApp and check your restored chats
If no backup appears, create a backup on the old phone first
On Android, go to WhatsApp Settings, Chats, Chat backup, then Back up to Google Drive
On iPhone, go to WhatsApp Settings, Chats, Chat Backup, then Back Up Now