diff --git a/docs/kittens/choose-files.rst b/docs/kittens/choose-files.rst
index 1bde11733..1a0f3ed34 100644
--- a/docs/kittens/choose-files.rst
+++ b/docs/kittens/choose-files.rst
@@ -46,10 +46,15 @@ chosen in a command line, use, for example::
 
     some-command $(kitten choose-file)
 
-Note, that the above may not work in a complicated pipeline as it performs
+Note that the above may not work in a complicated pipeline as it performs
 terminal I/O and needs exclusive access to the tty device while choosing a
 file.
 
+.. note:: For content previews, this kitten uses some external programs. In
+   particular `ffmpeg <https://www.ffmpeg.org/>`__ is needed for video
+   previews and `calibre <https://calibre-ebook.com>`__ is needed
+   for ebook metadata and cover preiews.
+
 Creating shortcuts to favorite/frequently used directories
 ------------------------------------------------------------