Your mobile device's screen normally emits a blue light that's fine for daytime use but can disrupt your sleep at night. That's because blue light stimulates your brain and fools it into thinking it's daytime, potentially keeping you awake if you use your device before bedtime. There are some studies that have found blue light may not deserve its reputation as a sleep-sucking vampire, but limiting your exposure before bedtime is still worth trying, especially if you have difficulty falling asleep. Your iPhone, iPad, and Windows 10 devices have a feature called Night Shift for changing the color temperature of the screen. Many Android devices also offer a built-in Blue Light feature, and a variety of third-party utility apps get the job done, too. Here’s how to control the blue light on your device.