PNG is lossless, so the savings come from reducing redundant colour rather than discarding detail. Transparency is preserved throughout. Output is preset to PNG below.
Output preset to PNG. Transparency is kept.
JPEG and WebP are lossy: they discard information the eye is unlikely to notice, which is why a quality slider exists. PNG is lossless — every pixel comes back exactly as it went in.
That means PNG compression works by finding redundancy rather than by throwing anything away, principally by reducing the number of distinct colours in the palette. On a screenshot, a logo or a flat illustration there is a great deal of redundancy and the savings are large. On a photograph, where almost every pixel differs from its neighbour, there is very little to find.
This is why the quality slider is disabled when you select PNG. There is no quality to trade.
Photographs. A PNG photograph is routinely five to ten times larger than the same image as a well-made JPEG or WebP, for no visible benefit — the format is storing detail nobody can perceive.
If your PNG is a photograph and the file is large, the answer is not better PNG compression. It is a different format. Convert it to WebP and expect the file to shrink by 70% or more.
WebP does lossless as well as lossy, and its lossless mode beats PNG on almost every image — commonly by 25% or more — while keeping transparency intact.
If the file is destined for a website, converting PNG to WebP is nearly always the better move. Keep PNG when the file is going somewhere that expects it: an app store submission, a print workflow, a client handoff, an older CMS.
PNG compression is lossless, so quality is preserved exactly. The size reduction comes from reducing redundant colour information, which works well on graphics, screenshots and illustration, and only modestly on photographs.
Almost certainly because it is a photograph. PNG is a poor fit for photographic content — convert it to WebP or JPEG instead and expect a much larger reduction.
No. Transparency is preserved throughout, and it also survives conversion to WebP. Only JPEG cannot store transparency, and converting to JPEG will flatten it.
WebP for anything shown on a website — it is smaller and still supports transparency. Keep PNG when the destination specifically expects it, such as app store assets, print workflows or older content systems.