How me3 works

A plain-English tour. The technical version, with the specifications we follow, is on the security page.

1. 1. Set up on your phone

   Open me3.org.uk/app and choose a passphrase. Your phone makes its own keys and keeps them, encrypted with a key that only your passphrase unlocks. Nothing about you is sent to us — there is no account to create. You can add me3 to your home screen so it opens like an app.

2. 2. Add a friend once

   One of you taps Add a friend → Show my invite. The other scans the QR code (or opens the invite link). The invite carries the public keys needed for a secure first message, plus a one-time secret. It works once and runs out after seven days.

   Behind the scenes the two phones run X3DH, the key agreement Signal published, and end up sharing a secret that nobody else — including our server — knows.

   Meeting in person is safest. If you send an invite link through another app, anyone who sees the link first could use it, so check the safety number together afterwards.

3. 3. Every message gets a new key

   me3 uses the Double Ratchet, also published by Signal. Each message is locked with a fresh key that is thrown away after use, and the keys keep moving forward as you reply to each other. If someone stole today’s keys they still couldn’t read last week’s messages, and the conversation heals itself after a few messages back and forth.

4. 4. Mailboxes that keep changing

   Your phone drops encrypted messages into a “mailbox” on our server and your friend’s phone collects them. The mailbox number is worked out from your shared secret and changes every six hours, and each direction has its own. Our database never holds a fixed ID for you or a list of who talks to whom. Messages are deleted when collected, or after seven days.

   Your phone checks for new messages in one batch every 15 seconds or so, mixed in with some made-up mailbox numbers, and messages are padded to a few standard sizes so their length gives less away.

5. 5. Contact codes instead of names

   With discreet mode on, me3 shows each friend as a short code like K7QM-2XTA instead of the name you gave them. The code is calculated from the secret you two share and the time, so it changes every 30 seconds. Both your phones show the same code at the same moment, but it means nothing to anyone else — every pair of friends has its own secret.

   Handy if someone glances at your screen. It is not a replacement for the safety number (below).

6. 6. Check the safety number

   Each conversation has a 60-digit safety number made from both phones’ identity keys. Put your phones side by side: if the numbers match, nobody swapped keys on the way. Tap Mark as verified to remember it.

7. 7. Disappearing messages, lock and wipe

   You can set messages in a conversation to disappear after 5 minutes, an hour, a day or a week — the setting is shared with your friend’s phone. me3 locks itself after a few minutes in the background. If you need to, Wipe this device deletes every key and message at once, and you can choose to wipe automatically after 10 wrong passphrases.

   Disappearing messages can’t stop someone taking a screenshot or a photo of their screen.

What you need

A recent browser on a phone or computer (Chrome, Edge, Firefox or Safari). Scanning a QR code inside me3 works where the browser supports it (Chrome on Android, for example); otherwise scan with your camera app or paste the invite link.

Checked 20 October 2026.