Compress PNG images without losing transparency

Screenshots, logos, and flat graphics, made smaller. Transparency is preserved, and metadata is stripped on the way through.

PNG is lossless, so where does the saving come from

A PNG never throws away a pixel. Compressing one is therefore not a matter of quality, it is a matter of encoding the same pixels more efficiently. Most PNG files in the wild were written quickly by a tool that had no reason to try hard: a screenshot utility, a browser download, an export dialog. They can usually be re-encoded 20 to 40 percent smaller with every pixel identical.

The other saving is the palette. A PNG that uses fewer than 256 distinct colors, which describes most logos, icons, diagrams, and flat illustrations, can be stored as an indexed image with a color table instead of full 24 bit color. For that kind of graphic the file often drops by half or more, and because the original only ever contained those colors, nothing is lost. A photograph saved as a PNG gets almost no benefit from this, which brings us to the next point.

If your PNG is a photograph, it is the wrong format

PNG was designed for graphics with sharp edges and flat areas of color. It is very bad at photographs. A photo saved as a PNG is routinely five to ten times larger than the same photo saved as a JPEG at a quality nobody can tell apart, and no amount of PNG optimization will close that gap, because the format is doing exactly what it promises and storing every pixel exactly.

If the image on your page is a photograph and it is currently a PNG, the single most valuable thing you can do is change the format. Set the output to WebP or JPEG here and compress it again. On a typical photo you will see the file drop by 80 percent or more. Keep PNG for the cases where it earns its keep: transparency, screenshots of text, line art, and anything with hard edges you need to stay crisp.

Transparency, and what happens to it

The alpha channel is preserved. A PNG with a transparent background comes back with a transparent background, at the same edge quality. If you convert to WebP, transparency survives too, because WebP supports alpha. If you convert to JPEG, it cannot, because JPEG has no alpha channel, and transparent areas will be filled. That is a property of the format and not a choice we are making on your behalf, but it is worth knowing before you convert a logo.

Screenshots are the most common win

A full screen screenshot on a modern high density display is commonly 2 to 6 megabytes as a PNG. That is a real page-weight problem for documentation sites, product tours, and blog posts, and it is one of the most common reasons people land here. Screenshots compress well because they are mostly flat color and repeated structure. Expect a 30 to 50 percent reduction while staying lossless, and considerably more if you are willing to convert to WebP, which handles both flat regions and text edges better than PNG at the same visible quality.

PNG questions

Does compressing a PNG lose quality?

No. PNG compression here is lossless: the output has exactly the same pixels as the input, stored more efficiently. The only way to lose quality is to convert to a lossy format like JPEG or WebP, which is a separate choice you make with the format selector.

Will my transparent background survive?

Yes, as long as you keep the output as PNG or convert to WebP. Both support an alpha channel. JPEG does not support transparency at all, so converting a transparent PNG to JPEG will fill the transparent areas.

Why is my PNG still large after compressing?

Almost always because it is a photograph. PNG stores every pixel exactly, and photographs have millions of distinct colors, so there is little redundancy to exploit. Convert it to WebP or JPEG and it will drop dramatically.

Do you strip metadata from PNG files?

Yes, by default. Text chunks, color profiles beyond what is needed, and editing history are removed. That makes the file smaller and means an exported image is not carrying information you did not intend to publish.