Metadata is data about data. It describes the context of a communication or file without revealing its content.
Examples: who you called, when, for how long, from which location. Which email contacted which address and when. Where your phone was when a photo was taken.
Metadata is often more revealing than content and harder to protect. End-to-end encryption protects content. It does not protect the fact that you sent a message, to whom, when, or how often.
What it means in practice
Metadata is often more revealing than content. A photo taken in the field contains GPS coordinates, timestamp, and device model — none of which is visible in the image itself but all of which is embedded in the file. Email metadata shows who communicated with whom and when, even when the message content is encrypted. Stripping metadata before sharing files is a basic operational habit, not an advanced measure.
Related articles
A journalist was arrested because of an email. — How to secure communications in the field. — Your phone carrier sells your location data. — Social media evidence in divorce proceedings.