What the specification means in practice
The physical specification is the same square 51×51 mm as the US passport photo, and the head occupies the same 50% to 69% of the image height. What differs is the submission path. Non-immigrant applicants upload a digital image with the DS-160 form, and that file has to satisfy constraints the printed photo never sees — a strictly square aspect ratio, a pixel range, and a file size limit that is easy to breach with a modern phone camera.
The digital file requirements
The image must be square: height must equal width, exactly. Minimum acceptable dimensions are 600 × 600 pixels and the maximum is 1200 × 1200 pixels, and the file must be 240 kB or smaller. That last figure is the one that trips people up — a 1200 × 1200 photo straight out of a phone is routinely several megabytes, so it has to be re-compressed rather than merely resized.
If you are scanning an existing printed photo rather than shooting digitally, scan the 51 × 51 mm print at 300 pixels per inch, which the department also expresses as 12 pixels per millimetre. That produces an image at the lower end of the acceptable pixel range.
Immigrant visas still want paper
Applicants using Form DS-260 for an immigrant visa bring two identical printed photos to the interview rather than uploading them. They are the same 2 × 2 inch photos, printed on photo-quality paper, and they must be identical to each other — two separate frames from the same session are not acceptable.
Because the interview may be months after the form was filed, check the six-month recency rule against the interview date, not the filing date.
Glasses, expression and head coverings
As with the passport, eyeglasses are no longer allowed in new visa photos except under a documented medical exception, and then only if the frames do not cover the eyes and there is no glare, shadow or refraction obscuring them.
The expression must be neutral with both eyes open, taken in full-face view directly facing the camera against a plain white or off-white background. Head coverings are refused unless worn daily for religious purposes; they must not obscure the hairline or cast shadows on the face.
Photographing an infant for a visa
Child applicants need their own photo, and no other person may appear in it — no supporting hands, no parent in frame. The department’s own suggestion for babies is to lay the child on their back on a plain white or off-white sheet, which supports the head and supplies the background at the same time. Watch for shadows if you shoot from directly above.
For toddlers, covering a car seat with a plain white sheet gives the same result with more head support. Infants are allowed some latitude on expression and eye position that adults are not.
Before you upload
Check the four things that cause most upload failures: the image is exactly square, it is within 600–1200 pixels on each side, it is under 240 kB, and it has not been enhanced or altered in any way. The DS-160 tool will reject a file that fails the mechanical checks, but it cannot see a shadow behind your head or a pair of glasses — those are caught later, by a person, at a much greater cost in time.