Rationale:

 - Right now:

   - These pages' Markdown will be rendered when browsing our
     repository in the GitLab web interface

   - The .md extension is more common nowadays: GitHub, GitLab, and various
     other major players have settled on it. Let's get used to it.

 - If we decide to migrate our blueprints to GitLab (#18079),
   this will be a necessary first step.

doc/mat.md

+[[!tag archived]]
+
+[[!meta title="MAT"]]
+
+What is MAT?
+============
+
+MAT (Metadata Anonymisation Toolkit) is a toolkit that anonymizes and removes
+metadata from your files. It does this utilizing a library, a GUI application
+and, if you prefer, a CLI application.
+
+How does it work?
+=================
+
+Simply put, MAT removes all metadata from files leaving them empty.
+Unfortunately, watermarks and steganographic tags won’t be removed but unlike
+metadata being added by default by many utilities, watermarks are not usually
+inadvertently added and the original author will likely be aware of their
+existence. Basically, MAT will protect you from accidental metadata leakage,
+but not customized metadata specifically included to track down you, the
+author.
+
+Why do we care?
+===============
+
+Because just about every file being uploaded to the internet contains metadata.
+From Office documents to .flac audio files and beyond, they all have metadata
+embedded, and that metadata tells the world where, when, and most crucially,
+who uploaded it. This defeats the purpose of Tails and our ‘privacy for anyone,
+anywhere’ mantra.
+
+So, to ensure you stay anonymous, Tails comes with MAT included.
+
+Currently supported files include:
+
+  - Portable Network Graphics (.png)
+  - JPEG (.jpg, .jpeg, etc)
+  - Open Documents (.odt, .odx, .ods, etc)
+  - Office OpenXml (.docx, .pptx, .xlsx, etc)
+  - Tape ARchives (.tar, .tar.bz2, etc)
+  - MPEG AUdio (.mp3, .mp2, .mp1, etc)
+  - Ogg Vorbis (.ogg, etc)
+  - Free Lossless Audio Codec (.flac)
+  - Torrent (.torrent)
+
+MAT can be accessed via: Applications > System Tools in the Tails GUI.