Home
SelfControl is a free and open-source application for macOS that lets you block your own access to distracting websites, your mail servers, or anything else on the Internet. Just set a period of time to block for, add sites to your blocklist, and click "Start." Until that timer expires, you will be unable to access those sites—even if you restart your computer or delete the application.
To download SelfControl, go to selfcontrolapp.com
This is a wiki with extra information about SelfControl. Some good pages to start on:
SelfControl is a free and open-source project, licensed under the GPL. It's maintained on volunteer hours; there is no professional staff or organization maintaining SelfControl. Contributions from others are always welcome!