How to compress a PNG

Why PNGs are big, and why there is no slider

PNG stores every pixel exactly. It is great for screenshots, logos and graphics with sharp edges and transparency, but a photo saved as PNG can be several times the size of the same photo as a JPG. Because the format is lossless, programs that offer a quality slider usually offer it for other formats: Apple's Preview, for example, shows a quality control when you export as JPEG or JPEG-2000, as of October 2026, not for PNG.

Three honest ways to make a PNG smaller

There are only three levers, and each trades something.

• Use fewer colours. Most screenshots, logos and illustrations use far fewer than the 16 million colours a PNG can hold. Rewriting the image with a palette of 256 or fewer colours takes a fraction of the space, which is how tools like TinyPNG and pngquant work. Transparency can be kept.
• Make the picture smaller. Fewer pixels means fewer bytes. Preview on Mac can resize an image, and any editor can; see how to resize an image to exact pixels.
• Change the format. For a photo with no transparency, a JPG or WebP is far smaller than a PNG. The cost is that transparency is lost and JPG is lossy. Which image format to use explains when that is fine.

In the browser, without uploading

The compress PNG tool keeps the file a PNG and works on one or many files at once. Choose a level:

• Best quality (256 colours): the default, good for most images.
• Smaller (128 colours) and Smallest (64 colours): a smaller file, with more visible banding in smooth gradients.
• Lossless (pixels unchanged): every pixel kept; only a tighter way of storing them is tried.

Transparency is always kept, including soft edges, and animated PNGs keep every frame and its timing. If the result would not be smaller, you get the original back unchanged and the page says so.

Results depend a lot on the picture. On a synthetic 800 by 500 test image of a noisy colour gradient (775 KB), 256 colours gave 154 KB (80% smaller) and 64 colours gave 81.5 KB (89% smaller), while Lossless kept the original because it could not do better. A flat-colour 400 by 400 logo with soft transparent edges went from 16.7 KB to 7.8 KB (53% smaller). Your own images will differ, so check the result by eye.

Everything happens inside your browser tab, so the images never leave your device.

When to use something else

For a photo, the compress image tool or the image converter will usually do better than any PNG setting. For email and upload limits, read how to reduce image size for email and uploads.

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