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Why an Image Sometimes Gets Larger After Compression

Quick answer

Re-encoding an already-optimized image — or saving a photo as PNG — can add bytes instead of removing them. Keep the original when compression doesn't help.

Re-encoding an image doesn't always remove bytes. Three common reasons it grows:

Why it happens

  1. 1
    Already optimized. If a file was already compressed, encoding it again mostly adds overhead.
  2. 2
    Lossless PNG. PNG can't throw away detail, so a photographic PNG often gets bigger, not smaller — convert it to JPG or WebP instead.
  3. 3
    Quality set too high. Saving a JPG/WebP at near-100% quality can exceed the original's size.
Our compressor turns on “keep the original if compression makes the file larger” by default, so you never end up with a bigger file by accident.
Compress an image — Try it — the original is kept if it can't be beaten.

Troubleshooting

My PNG got bigger.
Convert the photo to JPG or WebP in Image Studio.
Barely any reduction.
The file is likely already optimized. Lower the quality a little, or resize the dimensions.

Sources

Last verified · reviewed rarely.

Change history
  • — Initial publication.

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