What end-to-end encryption actually means
Each device holds a private key that never leaves it. A message is locked with the recipient’s public key before it leaves your phone and can only be unlocked by their private key at the other end. WhatsApp relays the locked package without being able to open it. The practical consequence people find hardest to believe is genuine: when a court orders WhatsApp to hand over message content, it cannot, because it does not hold anything readable.

