Find your level.
Rest your phone screen-up on the surface you want to check. Tap Start level and allow motion access if asked. The bubble moves toward the higher side; bring it to the center to level both axes.
Use this for a quick, approximate check. A phone case or camera bump can affect the reading. Use a physical level when precision matters. Readings stay on your device.
What does “set this as zero” do?
It treats the phone's current position as your reference point. Put the phone on a surface you know is level before setting zero, or use it to compare two surfaces. Reset zero restores the sensor's original reference. Rotating the screen also resets the reference.
Why isn't the bubble moving?
Your device may not have an accessible motion sensor, or your browser may block it. Open this page directly in Safari or Chrome on your phone, allow motion access, then try again. A desktop computer usually cannot provide these readings.
How close counts as level?
The tool displays “Level” when the combined tilt is within 0.5° of the current reference. It measures surfaces with the phone lying nearly flat, up to 45° from horizontal. This is not a plumb or vertical-wall measurement tool.
More tools: Compass · Tally counter