Monocle for MacOS is described as 'Monocle is a sleek, minimalist app that removes distractions by blurring everything but your active window, giving you the focus you need. No window juggling—just the task at hand, with everything else calmly waiting. It’s like noise-canceling for your screen' and is an app in the office & productivity category. There are three alternatives to Monocle for MacOS for Mac. The best Monocle for MacOS alternative is Focus Window Highlighter, which is free. Other great apps like Monocle for MacOS are HazeOver and Focusdim.
Monocle removes the dim on the next focused app when you close one app. HazeOver does not and the developer says he will not add that feature. That's one reason Monocle is better.