About Bubble Level Online
Bubble Level Online turns the phone in your pocket into a working spirit level — in the browser, free, with nothing to install. It exists because the moment you need a level (frame in one hand, nail in the other) is exactly the moment you don't want to hunt an app store or a toolbox.
How it works
Your phone has an accelerometer that senses which way gravity pulls. The site reads it through the browser's standard motion APIs and shows the result as a classic bubble vial: lay the phone flat for surface mode (both axes at once) or stand it on an edge for edge mode, with a 0.1° readout and one-tap calibration. All of it runs on your device — sensor data never leaves your phone.
How accurate is it?
Honest answer: after calibration, typically within a fraction of a degree — comparable to an inexpensive hardware bubble level, and plenty for hanging pictures, leveling appliances, campers, and everyday DIY. It is not a substitute for a machinist's level or professional survey gear, and we won't pretend otherwise.
Why free?
Because a spirit level is a 30-second errand, not a subscription. The site may eventually show unobtrusive ads to cover its costs; the tool itself stays free.