How to block an application (facebook, messages) in Self Control I figured out how to do a while ago, but simply can't remember- how do I block computer applications such as twitter, facebook, and messages in self control?
You cannot block apps, as hinted in a github issue on their repository, only websites.

Onefocus is a similar app that seems to be able to do it. I have never tried it nor have any affiliation with it, so I cannot attest to its quality.