HOLD
REF
CAL
Drag the guides onto the edge you are checking
Waiting for sensors
This level reads your device's motion sensors. Grant access to begin.
How far the bubble travels for a given tilt.
The window that counts as level and triggers the lock.
Smoother reads settle slower but ignore hand shake.
Rest the device on a known-true surface, then zero. For best accuracy, zero again with the device rotated 180°.
Installed, Bubbler opens full screen and runs with no network.
Bubbler · offline ready
Nothing saved yet. Tap Save on the level to capture the current reading.
Surface is the bullseye vial. Lay the device flat on a shelf, table or appliance and both axes read at once. Edge is the bar vial: stand the device against a frame, post or picture and it reads the single axis you care about. Rest it on the short edge or the long edge, whichever suits the job. Bubbler works out which edge is on the work and turns the vial to match. In Auto it switches between the two for you as you tip the device past 45°.
Camera lays a true horizontal and a true plumb line over the live view. You do not have to hold the phone level: the pair counter-rotates by however much the phone is tilted, so the lines stay true to the world at all times, and they stay exactly square to each other. Slide them onto whatever you are checking and any gap that opens along a line is the error in the thing you are looking at, not in how you are holding the phone.
Drag near a line to move that one on its own, or drag anywhere else to move the pair together. Double tap to recentre. For the closest reading, aim roughly straight at the subject: pointing steeply up or down puts perspective between you and the answer.
No phone is perfectly square to its own sensors. Put the device on a surface you trust, then Zero. To cancel out error in the surface itself, zero once, rotate the device 180° in place, and zero again, and Bubbler averages the two.
Ref captures the current attitude as a new datum. Everything after that is reported as the difference from it, so you can match one surface to another that is not level, or measure the angle between two faces.
Hold freezes the reading so you can read it after taking the device off an awkward surface. Tap again to release.
Phone accelerometers are good to roughly a tenth of a degree once zeroed and held still. Let the numbers settle for a second, keep the device off vibrating machinery, and prefer the longest edge of the device against the work.
On Android, open the browser menu and choose Install app, or use the button in Settings. On iPhone and iPad the only route is Safari's own Share button, then Add to Home Screen; no web page is allowed to trigger that for you. Either way the page must be loaded over https, which is also what the motion sensors require.
Once installed Bubbler runs with no network at all. Nothing is uploaded; saved readings stay on the device.