Most passport photo rejections come down to a handful of repeated mistakes. Avoiding these first saves a resubmission later.
Using a size from the wrong country, or exporting at a low resolution that looks fine on screen but pixelates when printed, is the most frequent error. Always check the exact mm and pixel values for the destination country.
Natural light from one side or an overhead lamp often casts a soft shadow behind the head or shoulders. Even a faint shadow can fail an automated background check.
Most countries require a neutral expression with both eyes open and the mouth closed, facing the camera directly. A slight head tilt or a smile is enough to be rejected.
Many countries now disallow glasses entirely in passport photos due to glare and reflection issues. Hats and headwear are usually not allowed either, except for religious coverings that do not obscure the face.
Photos must usually be recent (within the last six months) and must not be digitally altered beyond cropping, resizing and background correction - heavy filters or skin retouching can cause a rejection.
Comparing a photo against the official size and background for the destination country, ideally with a tool built specifically for it, catches most of these issues before submission. Upass sets the size and background automatically so at least those two checks are already correct.