Whether this is a good idea depends entirely on what your picture is
Converting a PNG to a JPG is either one of the best things you can do to a file or a small act of vandalism, and which one it is has nothing to do with the tool. It depends on what the picture contains.
Measured on this page’s own encoder, with two PNGs of the same dimensions:
So this page looks at your file before it converts it. It counts how many distinct colours the picture actually contains — a photograph runs to thousands, a logo or a screenshot to a few dozen — encodes it once to see what it really saves, and then tells you whether JPEG is the right destination. That verdict is based on your picture, not on a general rule.
Why flat colour and text suffer, when photographs do not
JPEG’s trick is to discard the detail your eye is least likely to miss. It divides the picture into eight-by-eight blocks and describes each one as a set of frequencies, then throws away the highest of those — the fine, rapid changes.
In a photograph, the fine rapid changes are mostly noise and texture. Losing them is nearly invisible, which is why the saving is so enormous for so little apparent cost. The standard that defines all this, ITU-T T.81, was designed around exactly that observation.
A hard black-on-white edge is the opposite case. It is a rapid change — the sharpest one possible — so throwing away high frequencies blurs it, and the maths that reconstructs it overshoots on either side. That overshoot is the faint grey halo you see around text in a badly saved graphic. Measured here at quality 85, individual pixels along those edges shifted by up to 107 levels, while the picture’s average change was under 4. The damage is concentrated exactly where you look.
Meanwhile PNG, being lossless and very good at runs of identical colour, was already storing that graphic efficiently. There was little for JPEG to win.
Transparency has to become something
JPEG has no alpha channel. None. If your PNG has see-through areas, those pixels must be given a solid colour, and the only question is which.
Most tools pick white silently. White is usually right and occasionally very wrong — a white logo destined for a dark header comes back as a white rectangle. This page detects the transparency, tells you before converting, and lets you pick the colour. Choose it to match wherever the picture is going.
There is a failure mode worth knowing about, because it looks like a bug: some converters draw your picture onto a blank canvas and encode without filling it first. Unset canvas pixels are transparent black, so flattening them gives black. If a converted logo has ever come back on a black background, that is why.
If losing the transparency is unacceptable, JPEG is simply the wrong format. Keep the PNG, or use WebP, which carries transparency and is usually smaller than both.
Naming a size instead of guessing at a quality number
“Convert this PNG to a JPG under 200 KB” is one of the commonest real requirements — forms, uploads and submission portals all impose limits — and a quality slider is a poor way to satisfy it, because the same quality setting produces wildly different sizes on different pictures.
This page lets you state the size instead. It then searches for the answer: nine encodings, each one narrowing the range, converging on the highest quality that still fits. Measured on a photograph:
- asked for under 100 KB → 99.5 KB at quality 79
- asked for under 30 KB → 29.9 KB at quality 23
- asked for under 5 KB → 4.9 KB at quality 5
Each took well under a tenth of a second. And when a target genuinely cannot be reached — asked for 2 KB, the smallest that picture could be made was 5 KB — it says so and explains that the next step is fewer pixels rather than lower quality, which is a job for the Image Resizer.
Questions people ask about PNG to JPG
Will converting PNG to JPG reduce the quality?
Yes — JPEG is lossy by design, so something is always discarded. On a photograph at a sensible quality you will not see it. On text, screenshots or line art you will, as halos around every sharp edge.
Can I convert back to PNG afterwards to get the quality back?
No. Converting back gives you a large, faithful copy of the already-degraded JPEG. Keep the original PNG if you might need it. The JPG to PNG tool is for when you need the PNG container — usually for transparency — not for recovery.
What quality should I choose?
75 to 85 suits most photographs. Below about 70 the artefacts start to show in smooth gradients like skies and skin. The slider here reaches 10, which is far lower than most tools allow, for when you genuinely need a tiny file and can accept how it looks.
Why did my converted file come out bigger than the PNG?
Because the picture is the kind PNG stores well and JPEG stores badly — flat colour, few distinct shades, sharp edges. It is unusual but not rare, and the tool flags it rather than letting you discover it. That is a strong signal to keep the PNG.
What happened to my transparent background?
It became a solid colour, because JPEG cannot store transparency. You choose which colour in the tool above; the default is white. To keep the transparency you need PNG or WebP.
Can I convert several files at once?
Yes, up to 30, with the same settings. The verdict is measured on the first one to keep things quick, and each row reports its own before-and-after size.
Does converting remove the metadata?
Yes. The picture is redrawn to make the conversion, so the result carries pixels and nothing else — no camera details, no date, no GPS coordinates. A privacy gain if you are publishing, a loss if you were relying on it.
Is JPG or PNG better for a website?
Usually neither — WebP beats both for most web images, carrying transparency like PNG and compressing photographs like JPEG only better. Use the Universal Image Converter to see the three sizes for your own picture side by side before deciding.
Are my images uploaded?
No. Everything happens inside this page on your own machine. Nothing is sent anywhere and nothing is stored.
Where the facts on this page come from
- ITU-T T.81, the JPEG standard, on block-based frequency compression and the absence of any transparency channel.
- PNG Specification (Third Edition), W3C, on lossless compression and the alpha channel.
- MDN — image file types and formats, on which formats suit which pictures.
- MDN — HTMLCanvasElement.toBlob(), which performs the encoding here and takes the quality argument the size search adjusts.
- WebP, Google, and caniuse — WebP, for the alternative mentioned throughout.