Enter the darkness. Lucifer is a tiny menu bar app that allows you to quickly switch between Dark Mode and Light Mode in macOS Mojave and later. Switch modes with a single click. No need to tediously open System Preferences ever again!
Latest version 1.3.2, Released 25 Aug 2019.
Requires macOS 10.14 or later.
If Lucifer is not working, it is likely because the app does not have the correct permissions. Open System Preferences and navigate to "Security & Privacy" > "Privacy" > "Automation" and ensure you have allowed Lucifer access to "System Events" by checking the box.
If this does not work, try deleting and re-installing the app.