compresspng.org — Frequently Asked Questions

Open it in Preview, choose File → Export, and reduce the image or export as a different format — or use the tool on this page, which needs nothing installed. The handbook has the full walkthrough including Photos and Automator.

Paint can resize and re-save, and the Photos app can resize with a quality slider. Neither offers real palette reduction, which is where an online compressor does better. Windows 10 and 11 both work the same way here.

Use File → Export → Export As, select PNG, and enable Smaller File (8-bit). That switches to a 256-colour palette, which is the same technique this site uses. Save for Web (Legacy) gives finer control.

Flat graphics and screenshots commonly lose 60–80%. Lossless optimisation alone yields 5–15%. Photographic PNGs are the poor case and are better converted to WebP or JPEG.

For anything on the web, yes — images are usually the heaviest thing on a page. For archival masters or print originals, keep the untouched file and compress only the copies you publish.

Either use the tool on this page, or use software you already have: Preview on a Mac, Photos or Paint on Windows, Export As in Photoshop, or Export A Copy in GIMP. The guides on this site walk through each one.

Lossless re-packing does not change the image at all. Palette reduction does change it, but on graphics and screenshots the change is not visible. Photographs and smooth gradients are the cases where you might notice.

PNG stores an exact reproduction; JPEG throws away detail the eye is poor at noticing. For photographs that difference is roughly tenfold. For flat graphics and text, PNG is often the smaller and better-looking of the two.

No. The alpha channel is carried through every setting here.

Multiple files are supported in a single batch and are returned together. Very large total uploads are capped, so split an enormous folder into a few batches.

Not within one batch — a batch applies one setting to everything, which is usually what you want for a consistent set. Run a second batch for images that need different handling.

As a single archive when there is more than one, so you only click download once.

Almost always because it is a photograph, a very large canvas, or both. PNG stores photographic detail exactly, and exact is expensive.

No. The aspect ratio is preserved; only the scale changes, and only if the image exceeds 2560px on its longest edge.

It covers essentially every screen use, including high-density displays. Print work is the exception — keep the original for that.

It should not, and it does not here — the palette is built including the alpha channel. What crude tools damage is the smoothness of semi-transparent edges, which is why this preset stays gentle.

Too few palette entries were left for the partially transparent edge pixels, so the soft fade was quantised into hard steps. A gentler setting fixes it.

You can, but JPEG has no transparency, so the transparent areas will be filled with a solid colour. Use WebP if you need both transparency and a small file.

Usually yes, often substantially — and the gap widens the more photographic the image is.

Yes, a full alpha channel, exactly like PNG. That is what makes it a real replacement rather than a compromise.

In browsers, yes — support is universal in current versions. Some older desktop applications still cannot open it, so keep a PNG copy if the file has to travel outside the web.