WhatsApp's end-to-end encryption is available when you and the people you message use our app. Many messaging apps only encrypt messages between you and them, but WhatsApp's end-to-end encryption ensures only you and the person you're communicating with can read what is sent, and nobody in between, not even WhatsApp. This is because your messages are secured with a lock, and only the recipient and you have the special key needed to unlock and read them. For added protection, every message you send has its own unique lock and key. All of this happens automatically: no need to turn on settings or set up special secret chats to secure your messages.
Your messages should be in your hands. That's why WhatsApp doesn't store your messages on their servers once we deliver them, and end-to-end encryption means that WhatsApp and third parties can't read them anyway.
Read an in-depth technical explanation of WhatsApp's end-to-end encryption, developed in collaboration with Open Whisper Systems.