Converting JPG to PNG

Where JPG came from, and why it is like this

This is the direction people misunderstand most, so it is worth being blunt: converting JPG to PNG cannot improve the image. PNG's losslessness applies from the moment of conversion onwards, not retroactively. What you get is a perfect, exact, considerably larger copy of a photograph that has already been through JPEG's compression — artefacts faithfully preserved at higher fidelity than before.

Expect the file to grow, often by a factor of five to ten. PNG is looking for repetition, and a JPEG-decoded photograph has almost none: the compression has left every pixel slightly different from its neighbours, which is close to the worst possible input for a lossless compressor.

Is this conversion lossy?

Nothing is lost. That is the entire point of the format, and it is why the conversion is worth doing when it is worth doing: whatever state the image is in, PNG will freeze it there and no further degradation can accumulate.

The practical value of that shows up when an image is going to be edited. Every save of a JPEG re-runs the compression, so an image opened, cropped and saved five times has been through JPEG five times, and generation loss compounds visibly. Converting to PNG first stops the clock. The image does not get better, but it stops getting worse.

What happens to metadata, transparency and colour

EXIF is dropped. This is the consequence people notice, and here it is frequently the reason for the conversion rather than a side effect. A JPEG from a phone carries the camera model, the exposure settings, the timestamp and — unless the phone was told otherwise — the GPS coordinates of where the photograph was taken. The canvas conversion discards all of it.

The colour profile goes with it. If the JPEG was tagged Display P3, as photographs from recent iPhones are, the resulting PNG has no profile and will be interpreted as sRGB. Saturated colours will look flatter. On an image destined for a document or a form this rarely matters; on a photograph it can be visible.

Transparency is not gained. The output PNG has an alpha channel, but it is fully opaque, because the JPEG had nothing transparent in it. Converting to PNG does not remove a background — that requires editing the image, not changing its container.

Why people actually need this

Two situations, and they have nothing to do with each other.

The first is a specification. Some systems accept PNG and not JPEG — print workflows that want no compression artefacts, certain document management systems, and a surprising number of internal tools written by someone with a preference. The image is what it is; the container has to change.

The second is stripping location data. A photograph about to be posted publicly carries GPS coordinates accurate to a few metres, and the fastest reliable way to remove them without installing anything is to run the image through a conversion that cannot carry them. It works, though it is a side effect rather than a designed feature, and it costs you the file size.

What we measured

This conversion was run end to end before this page was written. Not "should work" — run, with the output checked:

And the ceilings measured for Image converter, the tool that performs it, on the hardware described on the limits page:

Not tested

The page also refuses files above 50 MB before it starts, which is a guard written into the tool rather than something the browser imposes. Why those are different.

When something else is the better answer

If the goal is removing metadata, use the metadata remover instead. It does the same job deliberately, tells you what it removed, and lets you keep the JPEG format and the small file size rather than paying a fivefold size increase for a privacy fix.

If the goal is editing without generation loss and the file will stay on your own machine, your editor's native format — or TIFF — is a better home than PNG, which was designed for the web rather than for editing.

If the goal is a smaller file, this conversion does the opposite and you want the compressor.