11 F.lux
Before the addition of Night Shift to the macOS platform in Sierra 10.12.14, Mac users only had a few options for filtering blue light on their computer’s display. F.lux is one such option. It’s been around, and it’s still around.
While its necessity has obviously decreased, it’s still a handy little app — particularly for users who aren’t running the latest macOS versions. Best yet, it has several other features baked in, like advanced hue options and a “dark room” mode for film photographers.