Upload portals enforce two numbers: pixel dimensions and file weight. The first is a property of the image. The second is a property of how the image was compressed, and confusing the two leads people to damage a perfectly good photograph.
The limits you are likely to meet
- US DV Lottery: square, at least 600 by 600 pixels, JPEG no larger than 240 KB.
- UK passport, digital: at least 600 by 750 pixels, up to 10 MB - generous, and rarely a problem.
- Singapore ICA: 400 by 514 pixels with its own weight cap.
- India Passport Seva: a fixed pixel size with a narrow file-weight window, including a minimum.
That last point catches people out. Some portals reject files that are too small as well as too large, on the reasoning that a very light file has been compressed so hard the detail is gone.
Why a limit exists at all
Partly storage and bandwidth at scale - the DV Lottery receives millions of entries in a few weeks. Partly validation: a file weight window is a crude but effective proxy for "a real photograph at roughly the expected quality", and it filters out both enormous camera originals and heavily degraded ones.
The wrong way to get under the limit
Reducing pixel dimensions. Going from 600 by 600 to 400 by 400 certainly makes the file smaller and immediately fails the dimension rule. The two requirements have to be satisfied simultaneously.
Screenshotting the photo. It changes the pixel size to whatever your screen is, usually strips the colour profile, and re-compresses an already compressed image.
Emailing it to yourself. Mail clients helpfully resize attachments. The file that arrives is not the file you sent.
Crushing the JPEG quality. This is the right lever pulled too hard. Below a certain quality, blocking artefacts appear around the eyes and along the hair edge, and sharpness checks - which authorities do run - start to fail.
The right way
Keep the pixel dimensions exactly as specified, and tune the JPEG quality until the file lands inside the window. For a 600 by 600 portrait, 240 KB is comfortable: a quality setting in the region of 85 to 92 typically produces 150 to 250 KB with no visible artefacts.
The other lever, used before quality, is what is in the frame. A photo cropped to the specification is mostly a face on a plain background, and a plain background compresses to almost nothing. A busy original crops down to a much lighter file than it started as.
Things that quietly add weight
- An embedded colour profile is small but not free.
- A full-size EXIF thumbnail can add tens of kilobytes.
- Camera metadata, including lens data and, on a phone, GPS coordinates - which is also a privacy reason to strip it before uploading to any portal.
IDShot exports at the exact pixel size the portal asks for and tunes the JPEG so the file lands inside its weight window, keeping the sRGB tag and the DPI and dropping location and camera metadata.