I've featured Safe Eyes for Linux before so this one is for Windows users. We read more and more about blue light filters (and it also being recently debunked) to avoid eye strain, but the most important preventions are taking forced breaks every 20 minutes, not sitting too close to the screen, having correct eye focus, and not having the brightness set too high.
Eyes Guard will allow you to enable forced breaks. Another good alternative for Windows (not open source) is called Eye Saver which in addition has anti flicker and blue light filter options too.
👀 Windows Application for protecting your eyes. Contribute to avestura/EyesGuard development by creating an account on GitHub.