The best alternatives to NightOwl are Fireball Studio, Night Eye, and Luna. If these 3 options don't work for you, we've listed a few more alternatives below.
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Replace numerous apps and settings with One Switch. A time-saver for Mac, the app allows to access the key switchers like toggling between Dark/Light modes and managing AirPods connection. For convenience, set the app to show custom toggles in your menu bar and disable those you don’t use regularly. Fitting your flow, always.
Night Eye is a browser extension that enables dark mode on any website you visit. It does not ruin your browsing experience by simply inverting images.
I've built this app in my spare time to resolve my frustration with Windows 10 for not having automatic theme switcher. This may be included in the next releases of Windows 10 but for now here is Luna! Hope this app is useful for other people as well 😊