What is metadata?

Metadata is "data about data" or "information about information" that is embedded in computer files, usually automatically. Metadata is used to describe, identify, categorize, and sort files.

However, metadata can also be used to deanonymize users and expose private information.

Examples of metadata include:

  • In image files:
    • the location where a photo was taken
    • the date and time a photo was taken
    • the model and serial number of the camera used to take a photo
  • In text document files:
    • the author of the document
    • changes to the document

To learn more about how metadata can be used to identify and reveal personal information, see Behind the Data: Investigating metadata.

Removing metadata from files

Tails includes mat2 so you can remove metadata from files before you publish or share them.

mat2 works on many file formats, including:

  • image files, such as .jpeg, .png, and .gif
  • LibreOffice files, such as .odt and .ods
  • Microsoft Office documents, such as .docx, .xlsx, and .pptx
  • audio files, such as .mp3, .flac, and .ogg
  • video files, such as .mp4 and .avi
  • archive files, such as .zip and .tar

To use mat2 to remove metadata from your files:

  1. Open the Files browser.

  2. Navigate to the folder containing the files that you want to remove metadata from.

  3. Select the files that you want to remove metadata from.

  4. Right-click (on Mac, click with two fingers) on the files and choose Remove metadata.

It is impossible to reliably find and remove all metadata in complex file formats. For example, Microsoft Office documents can contain embedded images, audio, and other files containing their own metadata that mat2 cannot remove.

You should run mat2 on any files before you embed them into another document.

Also, you should save files in simpler formats whenever possible. For example, instead of saving a text document as a .docx file, you can save the document as a plain .txt file.