Why Your Compressed Image Got Bigger

You ran your image through a compressor and the output is larger than the input. It feels broken, but it is actually a well-known edge case. Here is why it happens and what to do about it.

The three reasons compressed files grow

First: format mismatch. Converting a small, optimized PNG to WebP or JPEG can produce a larger file because the target codec adds its own overhead — headers, color profiles, metadata. If the source was already well-compressed, there is nothing left to squeeze.

Second: the image is tiny. Compression algorithms need patterns to exploit. A 5 KB icon or a 1 KB favicon has so little data that the codec overhead alone can exceed the savings. Below roughly 10 KB, compression often breaks even or loses.

Third: lossless-to-lossy mismatch. Feeding a screenshot (few colours, sharp edges) through JPEG compression can bloat it because JPEG is optimised for photographs with gradual colour changes, not flat-colour graphics.

How to fix it

Stay in the same format. If the source is PNG, compress as PNG first. Only convert formats when you have a specific reason — like needing JPEG for a form upload.

Lower the quality slider. At 80 % quality most photos are visually identical to the original but 40–60 % smaller. MiniPx tries multiple quality levels automatically and picks the smallest output.

Resize before compressing. A 4000 × 3000 photo compressed to 80 % quality will always be larger than the same photo resized to 1920 × 1440 first. Fewer pixels means fewer bytes.

MiniPx handles all of this automatically. Drop your image in and MiniPx tries multiple quality levels and formats behind the scenes, always returning the smallest file that still looks good.

Frequently asked questions

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