Blue light is a harmful light that gets emitted by modern day devices. Almost anything with a display and touch screen interface uses blue light.
Solutions for Android device:
Nowadays, devices comes shipped with “night mode” (or similar) option which acts as a blue light filter.
If your device doesn’t support that feature, you can install third party applications. Playstore offers a large range of apps. The best one so far is “Twilight” by “Urbandroid Team” (having more than 5 million downloads and a 4.6 rating). It offers a lot of features. It is a must for phones these days. Another good blue light filter app is “Blue Light Filter – Night Mode” from “Leap Fitness Group” having more than a million downloads and a 4.7 rating).
Solutions for Windows PC:
Windows doesn’t have tons of apps but sure has some handy ones. f.lux is so far the most popular and trendy blue light filter for windows pc. This one supports Mac too. A secondary options is the SunsetScreen for Windows only.
Solutions for ios devices:
Ios 9.3 and above devices have a Night Shift feature which is literally the same blue light filter. This can be enabled from the control center using its icon. The Night Shift settings can be found in Settings>Display & Brightness>Night Shift. In case your ios device doesn’t support Night Shift, there is a third party app called f.lux .