PNG to JPG
Image Tools · Updated
Going from PNG to JPG is where the file gets dramatically smaller and where two decisions have to be made. JPEG is lossy, so you choose how much detail to trade for size; and JPEG has no alpha channel, so every transparent pixel has to become some actual colour. Both choices are yours here, and both are permanent in the file that comes out.
How to use the png to jpg
- 1Choose your PNG files, or drop them onto the box.
- 2Set the JPEG quality. Eighty-five is a sensible default; the note under the slider explains what happens above and below it.
- 3Pick the colour for transparent areas. White suits most documents; match your page background if the image will sit on one.
- 4Check the size comparison — a large reduction is the normal outcome.
- 5Download each file. Keep the PNGs: this conversion cannot be reversed by converting back.
Examples
A screenshot for email
- Input
- A 3.4 MB PNG screenshot at quality 85
- Result
- About 320 KB
A tenfold reduction. Look closely at the text afterwards — JPEG puts faint halos around sharp black-on-white edges, which is the trade being made.
A logo with a transparent background
- Input
- A PNG logo, background set to white
- Result
- A JPG with the logo on a solid white rectangle
The transparency is gone for good. Placed on a coloured page, that white box will show — which is the reason the colour picker is there.
The same image at two qualities
- Input
- One PNG converted at 95 and again at 60
- Result
- Roughly three times the file size at 95, for a difference most people cannot see
The size curve steepens sharply above about 90 while the visible gain flattens, which is why 85 is the usual recommendation.
About the png to jpg
The two things JPEG cannot do
JPEG is a superb format for photographs and it has two hard limitations that matter every time a PNG is converted into one. It cannot store transparency, and it cannot store anything exactly.
The transparency problem is absolute rather than a quality setting. A PNG's alpha channel records how see-through each pixel is; JPEG has nowhere to put that, so the image must be flattened onto a background before encoding. This is a genuine decision, not a technicality — a logo flattened onto white looks correct on a white page and wrong on every other one, and there is no way to change it afterwards without going back to the PNG.
The lossy part is the trade JPEG exists to make. It converts the image into frequency components and discards the ones the eye is least sensitive to, which is why a photograph compresses ten to one with no visible difference. The same mechanism is what damages text and line art: a hard black-on-white edge is made of exactly the high-frequency information JPEG is designed to throw away, which is why converted screenshots acquire faint halos around their letters.
Choosing a quality setting
The quality slider is not a percentage of anything visible. It sets how aggressively the encoder quantises those frequency components, and the relationship between the number and the file size is steeply non-linear. Between 90 and 100 the file can double for a difference that is invisible on a screen; between 70 and 85 the size moves modestly and the image stays clean; below about 60 the eight-by-eight blocks JPEG works in start to become visible, first around edges and then everywhere.
What content you are converting matters as much as the number. Photographs tolerate aggressive compression well, because the detail being discarded is buried in texture. Flat colour, screenshots, charts and anything containing text degrade visibly much sooner, and are often better left as PNG — the size comparison on this page will usually make that obvious by showing little or no saving.
One habit worth keeping: convert once, at the end. Every JPEG save re-quantises the image, so an edit-save-edit-save cycle in JPEG accumulates damage that never appears in a single conversion. Keep the PNG as the working copy and produce the JPEG when you need to send or publish it.