This article explains WhatsApp's end-to-end encryption and how you can use it to ensure that your messages and calls are secure. Release notes: Tested on Android 10.9 and iOS 13.12 with WhatsApp versions 2.20.27 / 2.20.21, respectively.
According to the WhatsApp FAQ page, “When end-to-end encrypted, your messages, photos, videos, voice messages, documents, status updates, and calls are protected from falling into the wrong hands.” Only you and the person you’re connecting with can read texts, view documents, or hear your voice. Not even WhatsApp can listen in. With end-to-end encryption, both sides have a lock and key built into the software, which locks and unlocks on both sides simultaneously, keeping prying eyes out.
WhatsApp claims that every chat has a unique lock and key to keep everything safe. You don’t need any special hardware or software and you don’t have to turn anything on, it’s built in.
They do offer one caveat, however. When you connect to a company using end-to-end encryption, anyone within that company can share the connection and see messages. Additionally, if the company outsources its communications to another company, that vendor can see, store, and access messages sent through their system. How this is handled depends on the company’s own privacy policy.