Restrictions How-to?

Can anyone tell me how Restrictions works, I’m looking for a way to NOT download .mkv files.

If I enter MKV in the “must not contain” field, will Sonarr look only in the torrent name for MKV or will it also look at the files in the torrent ?

thanks

It will only look at the torrent name (or for nzbs, the nzb name).