End-to-end encryption keys on Messenger

All end-to-end encrypted chats on Messenger are secure. Your messages are encrypted whether or not you compare keys.
Every device in an end-to-end encrypted chat has a special key that’s used to protect the conversation. No one can read your encrypted messages except the people who have these keys - not even Meta.
You and whoever you’re talking to in an end-to-end encrypted conversation are the only people who have unique and matching keys that can access the conversation.
Why your keys might change
Keys can change for several reasons. Keep in mind that not all key changes mean something’s wrong. For example, a new key can show up when someone reinstalls the app on their device.
Keys also change when someone:
  • Uninstalls the app.
  • Resets their phone.
  • Clears their app data.
When keys change, you’ll get a security alert in the conversation. Learn more about security alerts.
View and compare your keys
View your keys
  1. Open an end-to-end encrypted chat with someone.
  2. Click their name at the top.
  3. Click End-to-end encryption keys.
Compare your keys
  1. On your device, tap You. Your friend should tap your name to show the device keys for you on their device.
  2. Compare the keys that your friend sees for you with the keys that you see for yourself.
If the keys match, you know the conversation is secure between these devices.
Here’s an example:
  • Alyssa taps You on her phone and sees 123.
  • Her friend Brandon taps her name on his phone, and he sees 123.
  • This means that the keys for Alyssa and Brandon match, so they know their conversation is secure on these devices.
  • Brandon should do the same thing to ensure that the chat is secure for him too.
The safest way to compare keys is in person, but you can also read the numbers out loud over an audio or video call.
Other ways you can secure your Messenger chat
Before you manually compare keys, you can:
  • Check your keys to see all the devices you've used in each end-to-end encrypted chat.
  • Count the number of keys you have for a friend and compare it to the number of keys that your friend has for themselves.
  • Log out of any device you don't recognize to remove it from the end-to-end encrypted chat.
Note: If the number of keys for you and your friend doesn't match, it may mean that your device has been offline for a while. You can check that the chat is secure by sending your friend a message and seeing if the keys change. If you're ever unsure if the chat is safe, you should log out of devices you don’t recognize.
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