1. File size — too big or too small
The most common failure. Forms state a ceiling ("under 50KB") or, less obviously, a floor ("20KB to 50KB") — files below the minimum fail just as hard as those above it. Use Compress to Exact KB for ceilings, or Increase Image Size if your file is too small.
2. Wrong dimensions
A form asking for "3.5cm × 4.5cm" or "600×600px" will reject a correctly-sized-in-KB file if the pixel dimensions don't match. Government forms often specify both a physical size and a DPI — get the pixel math right on the Dimensions tab, which converts cm/mm/inch to exact pixels automatically.
3. Wrong format
JPG, JPEG, and JPG-renamed-as-PNG are not interchangeable to a strict validator. If a form says "JPEG only" and your file is a PNG (even one renamed with a .jpg extension), some systems detect the true format and reject it. Use the Convert tab to genuinely re-encode, not just rename.
4. Background or framing rules
This one a compressor can't fix automatically — plain white background, no glasses, no headwear, face-only framing. These are photography rules, not file rules. Retake the photo against a plain wall if your form specifies a background colour.
Frequently asked questions
My file meets the KB limit but still gets rejected. Why?
Check dimensions and format next — a correctly-sized file in the wrong pixel dimensions or format fails just as often as an oversized one.
Is there one tool that fixes all four issues?
Dimensions and format are both handled by PixKB's engine in one pass. Background and framing require retaking the photo — no compressor can add a white background after the fact.