Spirit Level
Lay your phone flat on a surface — the bubble centers when it's level. Works on phones and tablets with tilt sensors.
How to use it
Set your phone flat on the surface you're checking, screen facing up. The dot in the center moves as you tilt the device — green and centered means level. If your phone's sensors are slightly off, tap "Calibrate" while resting on a surface you know is flat, and readings will zero out from there.
Frequently asked questions
Does this work on desktop computers?
No — it needs a phone or tablet's built-in tilt sensors, which desktops and laptops don't have.
Why does iPhone ask for motion permission?
iOS requires an explicit tap to grant motion sensor access for privacy. Tap "Enable sensors" and allow the prompt.
How accurate is a phone-based level?
Fine for hanging a picture or checking a shelf — not precise enough for construction-grade work. Calibrate on a known-flat surface first.