WhatsApp has no private chat mode. Every message is e2e encrypted. If you switch devices, other clients will use the old keys until they have received the new

WhatsApp has no private chat mode. Every message is e2e encrypted. If you switch devices, other clients will use the old keys until they have received the new one (and then they will silently re-encrypt and resend undelivered messages, something WhatsApp was heavily criticized for).