Stand square to the wall — directly in front of what you are checking, not off to one side — and fill the frame with the edge itself. HangTrue reads the angle in the photo, so if you shoot from an angle, perspective tilts the edge and the reading tilts with it.
Under 0.3° is true: that is roughly 5 mm out across a metre, which is the point at which people stop noticing. Between 0.3° and 1° is slightly out — visible if you look for it. Over 1° is visibly crooked.
An angle is hard to act on, so HangTrue converts it. Set the slider to how wide the object is — the distance between the two ends you would actually adjust — and it tells you how far one end has to move. A 3° tilt across a 600 mm frame is about 34 mm.
Use Level for anything that should run horizontally: pictures, shelves, blinds, worktops. Use Plumb for anything that should run vertically: door frames, posts, wallpaper seams, the uprights of a bookcase.
The edge needs to stand out from what is behind it. A white frame on a white wall in flat light gives the app very little to measure. Get closer, or shoot it where the light gives the edge some contrast.
Everything strong in the photo is running more than 20° away from the reference you chose. Either the phone was held at an angle, or you want the other reference — try Plumb instead of Level, or the reverse.
When the edges in a photo disagree with each other — a busy scene, several objects at different angles — HangTrue says so rather than presenting a confident number it cannot support. A closer shot of one long edge will give a firmer answer.
No. HangTrue only reads. It does not edit, crop, save, copy or upload anything, and it never writes to your photo library.
The ad-free unlock is a one-time purchase tied to your Apple ID. On a new device, open HangTrue Pro from Settings and tap Restore purchase.