← Glossary
Metadata
The data about your data — who, when, where, how big — that often leaks more than the message content itself.
Metadata is everything around your message except the message body. It includes: who sent and received, the time and timezone, the IP address each side connected from, how big the message was, what device sent it, and how often the same pair communicates.
Even with perfect E2EE on the body, metadata can reveal a lot. "These two phone numbers exchanged 200 messages over three nights" is a story with no message content needed. The CIA's former director Michael Hayden famously said "we kill people based on metadata."
Modern privacy tools differ in their metadata story. Signal collects the bare minimum (timestamps + Sealed Sender). SimpleX has no user identifiers, so the contact graph is invisible to the server. Most messaging apps (WhatsApp, Telegram, Messenger) collect rich metadata regardless of E2EE on the body.