PNG compressor — free online tool

Shrink PNG files without changing a pixel: lossless optimization at level 3 keeps transparency and exact colors. No quality slider by design.

Compress images

Control quality, size, and format in one batch.

What to know

PNG compression here is lossless. A PNG file is a stream of filtered, deflate-compressed rows, and an optimizer can often find a better filter choice and a tighter encoding for the very same pixels. The tool runs one at effort level 3, without interlacing, and without touching the colors hidden under fully transparent pixels. Decoding the result gives you exactly the image you started with.

That is why there is no quality slider on this page. The savings come from smarter packing, not from throwing detail away, and they vary a great deal: flat graphics, UI screenshots and diagrams with large uniform areas shrink well, while a PNG that contains a photograph often barely moves, because noisy pixels leave nothing to pack.

The lossless path applies only when a PNG goes in and a PNG comes out with no resizing. If you tick Resize before compressing, or drop a JPG or WebP while PNG is the output, the file is redrawn on a canvas and saved as a plain PNG, and the optimizer is skipped. A photograph saved that way is usually larger than the JPG it came from.

If the optimized file is not smaller than your original, the original is handed back unchanged. When a PNG stays big because it is a photo, the better move is to convert it to WebP or JPG instead of compressing it further.

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How to use PNG compressor — free online tool
  1. Drop PNG files into the page; the output format is locked to PNG.
  2. Leave Resize before compressing unticked so the lossless optimizer runs.
  3. Run it and read the size column; entries marked as kept original were already compact.
  4. Download the optimized PNGs and, if they are still large photos, try the PNG to WebP converter.

Quick answers

Does compressing a PNG reduce its quality?

No. Level 3 optimization is lossless: it rewrites the compressed data, and every pixel and the alpha channel decode to the same values as before.

Why did my PNG barely get smaller?

Photographic or noisy PNGs have little redundancy to remove. The format suits flat graphics; for photos, WebP or JPG gives far larger savings.

What does ticking Resize before compressing do to the result?

The image is redrawn on a canvas at the new size and saved as a normal PNG. That path does not use the optimizer, so combine resizing with a second pass if you need both.

Is transparency kept?

Yes. The optimizer leaves the alpha channel and the colors under transparent pixels alone.