Focus (for ChromeOS) is described as 'With the touch a button, block distracting websites and get back your time on the internet'. There are more than 25 alternatives to Focus (for ChromeOS) for a variety of platforms, including Mac, Windows, Android, Google Chrome and Linux. The best alternative is LeechBlock, which is both free and Open Source. Other great apps like Focus (for ChromeOS) are FocusMe (Paid), StayFocusd (Free), SelfControl (Free, Open Source) and Focus (Paid).
LeechBlock is a simple free productivity tool designed to block those time-wasting sites that can suck the life out of your working day. All you need to do is specify which sites to block and when to block them.
SelfControl is a free and open-source application for Mac OS X 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 blacklist, and click "Start.
Focus is a Mac app that blocks distracting websites (like Facebook and Reddit) and applications, so you can improve your productivity. It has lots of awesome features like scheduling, showing motivational quotes on blocked pages, whitelisting and pomodoro support.
Stay focused helps you focus by restricting the daily usage of selected apps to the selected time. Spending too much of time Social Networking or Messaging Apps? Focus it and it will help you reduce the usage.