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.

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 Tails cannot remove.

You should remove metadata 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.

Removing metadata using Metadata Cleaner

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

Metadata Cleaner 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 open Metadata Cleaner choose Applications ▸ Accessories  ▸ Metadata Cleaner.

Removing metadata from the command line

Metadata Cleaner is a graphical interface for mat2.

You can also use mat2 directly on the command line:

  1. Open a Terminal.

  2. Execute the following command.

    Replace file.ext with a path to the file that you want to clean.

    mat2 file.ext

  3. After mat2 finishes, a copy of your file without metadata is available as file.cleaned.ext.