What this measures, and what it cannot
Four things, all from the outline of your mouth and the pixels inside it. Shade compares the brightness and yellowness of your teeth against a patch of your own skin below your lower lip. Symmetry compares the height of your two mouth corners. Width compares your mouth to your face. Tooth display compares the open part of your mouth to the whole mouth.
It cannot assess alignment, decay, gum health or bite. Those need a dentist looking at your actual teeth, and nothing here is dental advice. The 68 facial landmarks this uses describe the outline of your lips — they contain no information about individual teeth at all.
Why shade is the fragile one
Shade reads colour, and colour is mostly a property of the light you were standing in. Warm indoor bulbs push everything yellow. Your phone's automatic white balance shifts the whole frame to compensate, sometimes overcorrecting. Overexposure whitens teeth and skin together.
That is why the number is measured as a difference against your own skin rather than as an absolute colour: your face and your teeth are lit by the same light, so most of the illuminant cancels out. It also refuses to report a number at all when the mouth region is too dark, too blown out, or barely open — a missing measurement is more useful than a confident wrong one.
The practical consequence: a before-and-after pair taken under two different lights tells you nothing. If you want to track a change, take both photos in the same place, at the same time of day, facing the same window.
Why there is no single “good” number
Smile width and tooth display are proportions, not scores. A wide smile is not better than a narrow one; they are different faces. We report where yours sits because it is measurable, not because there is a target to hit. The only one of the four with a defensible direction is symmetry, and even there a small difference between mouth corners is extremely common and entirely unremarkable.
How this fits with the other tools
The smile analyser answers a different question: whether your smile reads as genuine, by checking for the eye involvement that separates a real smile from a posed one. The full face scan measures 17 facial-geometry metrics and gives you a validated Face Score percentile. This page is the narrowest of the three, and the only one that looks at your teeth.
If you are researching dental work, the honest sequence is worth knowing before you spend: read what whitening actually changes and the difference between veneers and crowns.
Your photo
On a desktop browser this runs entirely on your machine and the photo never leaves it. On a phone the image is sent to our scan server to locate the facial landmarks, processed in memory, and deleted immediately — it is never written to disk and never used to train anything.