Why is my PNG file so big?
A PNG is large because the format is lossless: it stores every pixel exactly, with no detail discarded. That is efficient for flat colour — logos, screenshots, diagrams — and very inefficient for photographs, where almost every pixel differs from its neighbour. A photo saved as PNG is commonly five to ten times larger than the same photo as WebP or JPG.
What actually makes a PNG large
PNG compresses by finding repetition. A screenshot of a settings panel is mostly identical runs of the same grey, so it compresses enormously. A photograph of a beach has a slightly different colour in every pixel, so there is almost nothing to collapse and the file stays near its raw size.
Pixel count matters just as much. File size scales with area, not width — a 4000px-wide image has four times the pixels of a 2000px one, not twice. Most oversized PNGs on the web are simply far larger in pixels than the space they are displayed in.
Transparency and colour depth add to it. A 16-bit-per-channel PNG with an alpha channel carries twice the data of an 8-bit one, and very few images visibly benefit from the extra depth.
The fix, in order of how much it saves
First, change format. If the image is a photograph, converting to WebP at 80–85% quality typically removes 70–90% of the bytes with no difference you can see at normal viewing size. This single step beats every other optimisation combined.
Second, reduce the pixel dimensions to what is actually displayed. Match the image to its slot on the page, then double it for retina screens: a 600px-wide slot wants a 1200px image and nothing more.
Third, if it must stay PNG — because you need lossless flat colour or guaranteed compatibility — reduce the dimensions and strip the unnecessary bit depth. There is no quality slider for PNG, because the format never throws detail away.
When to keep PNG anyway
Keep PNG for logos, icons, line art, screenshots containing text, and anything that needs sharp edges or transparency and will be re-edited later. JPG smears visible artefacts around hard edges and cannot store transparency at all.
Keep PNG when the file has to open anywhere without question — an email attachment, a print handoff, an upload to a system you do not control.