Mobile Sensors

Need to check direction while hiking or camping? The compass uses the device orientation sensor to show your current heading, and hanging furniture or a picture frame level is easier with the bubble level reading tilt from the motion sensor.

Without a tape measure, roughly gauge an object's length by holding the on-screen ruler up to it, and to check whether a place is genuinely loud, the sound meter estimates ambient noise in decibels using the microphone.

To check a new phone or monitor screen for defects, the dead pixel test cycles through full-color screens — red, green, blue, black, white — to reveal stuck or dead pixels, and the flashlight turns the camera flash or a bright screen into an instant light source.

A phone's compass can swing well off if it's inside a case with a magnet or sitting next to a speaker, so for an accurate heading, take the case off and move away from metal or magnetic objects before reading it again. The on-screen ruler's marks are only as accurate as the match between the screen's physical size and its reported resolution — some devices drift slightly depending on display-density settings, so treat it as a rough length check rather than a precise measurement. The dead pixel test can hide dim pixels if the room is bright, so dimming the room and maxing out screen brightness gives a more reliable read.