Free Online Image OptimizerGetting a photograph out of PNG
PNG stores every pixel exactly as given. For a logo or a screenshot of an interface that is precisely what you want. For a photograph it is close to the worst possible choice, and the file sizes make the point without much help: the same holiday snap can be five or six times heavier as a PNG than as a JPEG nobody could tell apart from it.
Lossless is a promise you rarely need kept
The reason PNG is so large on a photograph is that it refuses to throw anything away. Every subtle gradation across a sky is preserved perfectly, including the parts no eye will ever resolve. JPEG discards those on purpose, which is why it wins so heavily on this kind of content and loses on a chart with hard edges.
Most photographs end up as PNG by accident rather than intent — dragged off a web page, exported from a screenshot tool, or saved by software whose default nobody changed. PNG to JPG exists for that pile.
Give it the heavy files
Drop one in, or a batch. The picture appears on the stage and a single press does the rest.
Then read the figure above the table rather than trusting the idea in the abstract. It states what arrived, what came back, and the percentage between them, measured on your actual file rather than estimated from its type. Photographs routinely land somewhere between sixty and eighty-five per cent smaller. Something flat and graphic may barely move, and occasionally grows — which is the tool telling you it was already in the right format and you should keep the original.
Anything see-through has to become something
JPEG has no concept of transparency. If the PNG carried any — a cut-out product shot, a logo with nothing behind it — those areas cannot survive the crossing and are filled in.
That is the single reason to stop and think before converting. A photograph almost never has transparent regions, so this rarely bites; a graphic very often does. Where it matters, WebP keeps the transparency and most of the compression at once, and its own page is configured for exactly that.
Worth knowing
When to leave it alone
Screenshots of text, diagrams, line art, anything with large flat areas and hard boundaries: leave these as PNG. JPEG smears exactly the edges those depend on, and the artefacts around dark text on a pale ground are visible at ordinary viewing size. The format guide sets out which content suits which.
Quality, if you want to touch it
The default sits where the difference is very hard to see and the saving is already most of what is available. Pushing it higher costs a lot of bytes for very little; dropping it a long way shows up first in flat gradients and around sharp boundaries. Adjust it, look at the result, and judge with your eyes rather than the number.