How PNG to JPG conversion works
PNG and JPG compress in fundamentally different ways. PNG is lossless: it filters each row of pixels and packs them with DEFLATE, so the original pixels can be recovered exactly. JPG is lossy: it converts the image to luminance and colour channels, usually stores colour at reduced resolution, splits it into 8×8 blocks, applies a discrete cosine transform (DCT), and rounds away high-frequency detail the eye notices least. The quality setting controls how aggressively that rounding is done.
Here, the browser decodes your PNG at its full pixel size, paints it onto a canvas, and re-encodes the canvas as JPG. The image dimensions never change. The slider runs from 10% to 100% and starts at 90%, and moving it re-encodes immediately so the download button always shows the exact resulting file size.
What happens to transparency
JPG has no alpha channel. This converter first fills the canvas with solid white, then draws the PNG on top, so transparent pixels become white and semi-transparent edges, such as a soft drop shadow, blend toward white. A logo designed for a dark page will therefore look like a dark logo on a white box. If you need a different background, add it in an editor first, or keep the PNG.
Worked example
A 1920×1080 screenshot of a web page saved as PNG is typically 600 KB to 2 MB. Converted at 90%, it usually lands around 150 to 400 KB. At 70% it may drop to 80 to 200 KB with only slight softness around text. Photographs show the biggest gains: a 4000×3000 PNG export of 15 to 25 MB commonly becomes 1.5 to 4 MB as JPG. These figures are approximate and depend on image content.
When to convert, and when not to
| PNG | JPG | |
|---|---|---|
| Compression | Lossless | Lossy |
| Transparency | Yes | No |
| Best for | Screenshots, logos, text, flat colour | Photographs, gradients |
| Repeated saving | No degradation | Each re-save loses detail |
Common mistakes
- Converting text screenshots at low quality. JPG leaves faint speckles around sharp edges. Stay at 85% or higher for text, or keep PNG.
- Converting back and forth. Going JPG to PNG does not restore detail; the PNG simply stores the already-degraded pixels at a larger size. Keep your original PNG.
- Expecting metadata to survive. The image is re-drawn on a canvas, so embedded metadata is not copied to the output.
- One file at a time. This tool converts a single image per run and keeps your original file name with a
.jpgextension, for examplephoto.jpgfromphoto.png.
Need a smaller file without changing format? Try the Image Compressor, or change the pixel size with the Image Resizer. For the reverse direction, see JPG to PNG.