Metadata: what a messenger knows about you without reading a word
Arguments about messenger privacy almost always circle around encrypting content. That matters, but it is only half the picture. The other half is metadata: everything known about the fact that a conversation happened, apart from the words themselves. Metadata is usually not end-to-end encrypted even in apps that encrypt messages, because without it the server could not deliver anything to anyone.
What counts as metadata
The exact set depends on the app, but in some form nearly all of the following exists.
- Who talks to whom, and which groups you belong to.
- The precise timestamp of every message, and when you were online.
- Message size and attachment type: it is clear that you sent a photo even when nobody can see it.
- Your IP address, and with it your approximate location and network operator.
- Device model, operating system version and app version.
What can be reconstructed from it
From metadata alone, without a single word being read, a surprisingly detailed portrait emerges. The hours you sleep show up as gaps in activity. Your inner circle shows up in the frequency and length of exchanges. A job change shows up as one cluster of contacts fading while another appears. A trip shows up as a change of IP address.
Researchers often use one classic example: you do not need the content to draw conclusions, it is enough to know that someone called a clinic, then a close relative, then an insurance company. The whole story reconstructs itself from connection records alone.
Why a phone number amplifies all of this
Metadata becomes genuinely sensitive when there is something to attach it to. A phone number is the perfect key: it is usually registered to your legal identity, it is the same number your bank and your deliveries use, and it makes matching records across sources easy.
A messenger that does not ask for a number does not eliminate metadata, but it does remove the ready-made key to your identity. That is exactly why Chattr sign-up is anonymous.
What you can do yourself
Metadata cannot be eliminated entirely: without it there is nowhere to deliver a message. But how much of it accumulates about you is well within your control.
- Prefer apps that do not require a phone number and do not upload your entire address book.
- Keep separate parts of your life in separate accounts so they never merge into one contact graph.
- Turn off online status and read receipts where you can: it is the simplest way to stop broadcasting your daily rhythm.
- Do not grant contacts and location access by default, enable them only when a feature genuinely needs them.