Check the photo before you send it.
Five things go wrong most often: too small, dark, uneven background, soft focus, head in the wrong place. This page measures the first four and estimates the fifth, on your device.
Everything above runs on your device. Nothing is uploaded, and nothing is stored. These are estimates from pixel statistics, not a facial analysis: use them as a checklist, not a verdict.
Is the file big enough for the print size?
Is the face lit evenly, and not too dark?
Is the background plain and even?
Is the face in focus?
Roughly where the head sits in the frame.
What it measures, and what it cannot
Resolution, brightness, background flatness and sharpness are pixel statistics. They are computed from the file you drop in, in this tab, and they catch the four mistakes that send most photos back. They are also the four things a photo shop checks by eye.
What it cannot do is decide. A check can tell you the background is uneven; it cannot tell you whether your expression, glasses or head covering will be accepted. Treat a clean result as permission to stop worrying about the file, not as an approval.