diff --git a/system/default_programs.md b/system/default_programs.md
new file mode 100644
index 0000000..8aa3a9c
--- /dev/null
+++ b/system/default_programs.md
@@ -0,0 +1,29 @@
+---
+title: "Default Programs"
+tags: [ "Documentation", "Defaults", "Mime Type" ]
+---
+
+Install the package `xdg-utils`.
+
+In general, type these commands with `bash-completion`, and you'll see the right option.
+
+## Ask
+
+Ask what type of application opens an mkv file:
+
+> xdg-mime query default video/mkv
+
+Same with pdf:
+
+> xdg-mime query default application/pdf
+
+## Set
+
+Set the mime type of mp4 videos to mpv.
+
+> xdg-mime default mpv.desktop video/mp4
+
+### Alternative: File
+
+Look in `~/.config/mimeappps.list` to check and set.
+