PNG to JPG Converter
PNG stores every pixel exactly and supports transparency. JPG throws away detail the eye is bad at noticing and has no transparency at all. Converting between them is not a neutral reformat, it is a decision to trade fidelity and alpha for file size. Whether that is the right trade depends entirely on the image.
How to use it
- Drop in a .png file.
- The image is drawn to a canvas over a white background, then encoded as JPEG at quality 0.90.
- The .jpg downloads immediately.
Transparency becomes white, and you need to know that in advance
JPEG has no alpha channel. There is no encoding option, no quality setting, and no workaround that changes this. Every transparent pixel has to become an opaque colour during conversion, and something must decide which colour.
This converter fills the canvas with white before drawing the image. For a logo intended to sit on a white page, that is the correct and invisible result. For a logo designed for a dark header, you get a white rectangle around it, and for a soft drop shadow you get a grey smear where the semi-transparent pixels were blended against white.
If your image has meaningful transparency and the destination is not white, JPG is the wrong format. Convert to WebP instead, which supports alpha and compresses photographic content comparably well.
When JPG genuinely wins, and when it loses badly
JPEG compression works by transforming blocks of pixels into frequency components and discarding the high-frequency ones. This is extremely effective on content where colour varies smoothly and gradually, and destructive on content built from hard edges.
A rough guide to which format suits which image:
- Photographs, renders, and anything with natural gradients compress dramatically as JPG, often to a tenth of the PNG size, with no visible difference at quality 0.90.
- Screenshots containing text develop visible ringing around every letter. The artefacts are worst on small text against a flat background, which describes most UI screenshots.
- Line art, icons, and diagrams with large flat colour areas frequently come out larger as JPG than as PNG, while also looking worse. PNG compresses runs of identical pixels efficiently; JPEG has no equivalent advantage.
- Images with sharp colour boundaries, such as charts with solid fills, show colour bleeding along the edges because chroma is subsampled.
Quality, and why re-encoding accumulates damage
Encoding here runs at quality 0.90, which is high enough to be visually lossless on most photographic content while still delivering the large size reduction that motivates the conversion in the first place.
What quality does not do is undo previous damage. If the PNG was itself created from a JPEG, the compression artefacts from that first encode are now real pixel data, and this encode compresses them along with everything else. Each generation adds more. Where possible, convert from the original source rather than from an image that has already made the round trip.
At a glance
| Accepted input | .png |
|---|---|
| Output | .jpg at quality 0.90 |
| Transparency | Flattened onto a white background |
| Engine | Canvas 2D, browser native JPEG encoder |
Frequently asked questions
My transparent PNG now has a white box around it. Can that be fixed?
Not within JPG, because the format has no alpha channel at all. The white is what the transparency was flattened onto. Use WebP if you need both transparency and small files, or keep the PNG if the destination background varies.
Why is my JPG larger than the PNG was?
Your image is probably line art, an icon, or a screenshot. PNG compresses large areas of identical colour very efficiently, and JPEG cannot. If the source is not photographic, the conversion often costs you size as well as quality.
What quality setting is used?
0.90, which is high enough that most people cannot see the difference on photographic content, while still producing a substantially smaller file.
Does converting to JPG and back to PNG restore the original?
No. The detail discarded by JPEG is gone permanently. Converting back to PNG produces a lossless copy of the damaged image, which is larger than the JPG and no better looking.
Read more
Choosing an image format — Why the same photograph can be 40 KB or 4 MB depending on a single dropdown, and how to choose deliberately.