Forest is described as 'app to help you stay focused on your work. Whenever you want to concentrate, you can plant a seed in Forest. In the next 30 minutes, this small seed will gradually grow into a big tree' and is an app in the Office & Productivity category. There are more than 50 alternatives to Forest for a variety of platforms, including Mac, Android, Windows, Google Chrome and Linux. The best alternative is SelfControl, which is both free and Open Source. Other great apps like Forest are Cold Turkey (Freemium), LeechBlock (Free, Open Source), StayFocusd (Free) and Freedom (Paid).
Citrus is an app that actively blocks distractions before they ever get to you. Simply tell Citrus what distracts you, and when you want it blocked, and Citrus takes care of the rest! CItrus actively blocks your distractions as you work!.