When a PNG Is the Wrong Format
PNG is lossless, which is exactly right for screenshots, logos and diagrams and exactly wrong for photographs. A photo saved as PNG can easily be five times the size of the same picture as JPEG, with no visible benefit, because lossless compression has very little repetition to work with in a photographic image.
Converting to JPEG fixes that, at the cost of transparency and of some detail you will not see at normal viewing size.
How to Convert PNG to JPG
Unlike the reverse direction, this conversion has a quality setting, because JPEG is lossy.
- Drop your PNG files onto the box above.
- Set the quality. Around 80 to 85 is the usual choice for photographs and is visually indistinguishable at normal size.
- Note that transparency will be lost. JPEG has no alpha channel, so transparent areas are filled, normally with white.
- Compare the resulting size. A photographic PNG commonly drops to a fifth of its size or less.
- Check the result at full size, particularly around any text or sharp edges, which is where JPEG struggles.
- Download the JPG files. The PNGs you started from remain on your device unchanged.
What Happens to Transparency
JPEG cannot store transparency at all, the format has no alpha channel. When a PNG with transparent regions is converted, those regions have to become some colour, and white is the usual choice. A logo with a transparent background will therefore arrive on a white rectangle, which looks fine on a white page and obviously wrong on any other colour.
This is the single most common surprise in PNG-to-JPEG conversion, and it is not recoverable afterwards: once the transparency is flattened, the information about which pixels were transparent is gone. If the image needs to sit on varying backgrounds, keep it as PNG or convert to WebP, which supports transparency in both its lossy and lossless modes.
Which Format for Which Image
The choice depends far more on what the image contains than on what it currently is.
| Image type | Best format | Why |
|---|---|---|
| Photograph | JPEG or WebP | Lossy compression suits continuous tone |
| Screenshot with text | PNG | Sharp edges, JPEG produces halos |
| Logo or icon | PNG or SVG | Flat colour and usually transparency |
| Diagram, chart | PNG or SVG | Lines and flat fills compress well losslessly |
| Photo needing transparency | PNG or WebP | JPEG cannot store an alpha channel |
| Scanned document | JPEG at high quality | Photographic noise, large page area |
SVG belongs in this table for logos and diagrams because it is not pixels at all, it stays sharp at any size and is usually tiny. If the original artwork exists as a vector, using it directly beats any raster conversion.
The Conversion Is One-Way
JPEG compression is irreversible. Once a PNG has been converted, converting back gives you a PNG that stores the JPEG artefacts with perfect fidelity but does not restore the original detail. Keep the PNG if it is the only copy, and treat the JPEG as an export rather than a replacement.
It is also worth checking whether the PNG needed to be that large in the first place. Screenshots at full retina resolution are often twice the pixel dimensions they will ever be displayed at, and halving the dimensions may solve the size problem entirely while keeping the PNG format that suits the content.