What color reduction does to a PNG
PNG compression with a smaller color palette can reduce PNG file size, but it can change similar shades. PNG stores the chosen pixels without further loss; the color reduction happens before they are saved. Select Keep all colors to avoid palette reduction. For PNG compression with fewer colors, compare the result with the original before deciding which copy to use.
An icon with a few solid colors is a different task from a photograph containing thousands of subtle shades. Stronger PNG compression may suit the icon while making gradients in the photograph look stepped. Choose the palette for the content, then review PNG compression around edges, shading, and transparency. PNG compression is successful when the result remains suitable for its actual use.
Further reading: W3C: PNG colors, transparency, and lossless storage
Match the color palette to the artwork
Start with a larger color palette when the PNG contains subtle shading. Lower the color count gradually, watching the parts that define the image. A colored logo may depend on a small difference between two shades; a screenshot may depend on tiny text remaining legible. A smaller PNG file size should not erase the information the viewer came to see.
For transparent graphics, inspect the PNG over the background where it will appear. An edge that looks acceptable on white may be more visible against dark gray. Check soft shadows, rounded corners, and partially transparent details. Keeping PNG output allows transparency, but reducing the color palette can still change the appearance of those areas.
| PNG content | Inspect after compression | If the result changes too much |
|---|---|---|
| Icons and flat illustrations | Small shapes and boundaries between colors | Increase the number of colors |
| Screenshots with text | Thin strokes, punctuation, and colored text | Use a larger palette or keep the original |
| Soft shadows and gradients | Banding and changes around transparent edges | Keep more colors and compare on the final background |
| Photographs saved as PNG | Skin tones and smooth color transitions | Compare JPG or WebP if the destination accepts them |
Reduce PNG file size before changing dimensions
If a logo already has the right pixel dimensions, try PNG compression before resizing. Resizing a small logo merely to reduce PNG file size can make its lettering harder to read. Keep the original dimensions while comparing palette settings, then decide whether the smaller PNG is acceptable. The result size is measured from the downloaded file, not a predicted saving.
Large screenshots and oversized graphics may also benefit from smaller dimensions. A graphic intended for a narrow content area rarely needs every pixel of an enormous export. Set a reasonable maximum size when that suits the destination, while retaining the proportions. After resizing, inspect fine lines at the final size rather than assuming that a clean full-size original guarantees a clean smaller PNG.
Keep an original and compare a few meaningful versions
Avoid repeatedly compressing an already reduced PNG while searching for a better setting. Colors removed during one pass do not reappear when the next pass allows more colors. Returning to the original gives each comparison the same starting point. Preserve that original separately, particularly for logos, illustrations, or screenshots that may later need different dimensions.
- Add the original PNG and choose a color count appropriate to its shading and detail.
- Keep dimensions unchanged for the first pass unless the PNG is clearly oversized.
- Compare the PNG file size and check the image on the intended background.
- Try another palette from the original if the first result introduces noticeable changes.
- Download an individual PNG or package completed batch results into a ZIP.
PNG compression keeps the original when it cannot save space
PNG compression does not guarantee a smaller file. A simple original may already be compressed efficiently, and a new export can add overhead or represent the data differently. When a new export would not reduce PNG file size and no smaller dimensions were requested, the tool returns the original with a notice. If you requested a resize, the resized result is kept with its actual file size. The download is therefore not necessarily a newly compressed image. Check that notice before treating it as a smaller copy.
A hard KB ceiling may require a different format. When transparency is unnecessary, JPG can be an option for a photograph. WebP is another option where the receiving service accepts it. Do not change formats just to lower a number if the destination specifically asks for PNG. Its accepted formats and minimum dimensions matter as much as the upload limit.
Compress PNG: questions and answers
Is this PNG compression lossless?
No lossless guarantee applies. The color palette can be reduced, so pixels may change even though the output remains PNG. Keep the original if exact colors and pixel values are required.
Can PNG compression preserve transparency?
PNG output supports transparency. Check partially transparent edges and shadows after color reduction because their appearance can change. Compare against the background where the PNG will actually be used.
Why is the compressed PNG still large?
Detailed images, many colors, and large dimensions can keep PNG file size high. Try a smaller color palette or dimensions if acceptable. Some images are already compact, so further PNG compression may provide little benefit.
Do PNG images leave my browser?
No. Processing happens locally in your browser. Multiple PNG images can be processed together and downloaded individually or as a ZIP of completed results.