Common image format problems, and how to actually fix them

Most format problems people run into aren't mysterious — they're the same handful of causes recurring in different contexts. This is a rundown of the ones we see most often, and the specific fix for each.

"My transparent logo has a white box behind it"

This happens when a PNG (or WEBP) with an alpha channel is converted to JPG, which has no transparency support at all. Whatever converted it had to fill the transparent pixels with something, and it defaulted to white. The fix is either to keep the file as PNG or WEBP wherever it's used, or, if JPG is genuinely required, convert deliberately with a background colour chosen to match the destination — our PNG to JPG tool lets you set that colour explicitly instead of guessing.

"The upload form rejects my file"

• Wrong format accepted — some forms only take JPG or PNG; convert from WEBP, HEIC, BMP or TIFF to whichever is listed.
• File too large in bytes — resize dimensions down first, then compress; check the exact limit stated, not a guess.
• Wrong pixel dimensions — many document and photo forms enforce exact width/height or aspect ratio, not just a file size cap.
• Corrupted or partial file — re-export from the original source rather than re-uploading the same broken file.

"I renamed my file to .jpg in Finder or Explorer, and it still fails"

Changing a filename from `photo.heic` or `banner.webp` to `photo.jpg` only changes the label on disk — the bytes inside the file are still encoded as HEIC or WebP. Upload portals and image editors inspect the first few bytes of the file (the magic-byte signature, such as `FF D8 FF` for JPEG or `89 50 4E 47` for PNG) rather than trusting the filename. To change the actual format, run the file through a real decoder-and-encoder converter so a genuine JPEG or PNG binary stream is written.

"My iPhone photos won't open anywhere"

Recent iPhones save photos as HEIC by default, a format most non-Apple software and many websites don't support. The fix is to convert to JPG once, on export or in the tool of your choice — HEIC is a fine format for storage on the device, but a poor one for sharing anywhere outside the Apple ecosystem.

"My portrait photo looks upright on my phone, but uploads sideways"

Smartphones often record sensor pixels in landscape orientation (such as 4032 × 3024) and attach an EXIF Orientation tag (1–8) that tells modern apps to rotate the picture to 3024 × 4032 on screen. Older government portals, PDF generators, and legacy CMS uploaders ignore that metadata tag and render the raw sideways pixel grid. Opening the photo in our Rotate Image or Resize Image tool redraws the physical pixels upright and strips the ambiguous EXIF tag so the image displays identically everywhere.

"The image looks worse after I resaved it"

If the file is a JPG or WEBP, this is generation loss — every re-save of a lossy format discards a little more information, and it's cumulative and permanent. Keep an untouched original (ideally lossless, like PNG or the camera's raw file) and always export fresh copies from that original rather than editing the same lossy file repeatedly.

"Colours look different after converting"

This is usually an embedded colour profile (like Adobe RGB) being interpreted differently, or being stripped, during conversion. It's most noticeable on saturated reds and greens. If exact colour accuracy matters — brand colours, product photography — check that the tool preserves or correctly converts the colour profile, and verify the result against the original on a colour-calibrated screen rather than assuming any shift is a bug.