JPG, PNG or WebP?
Start with the picture and its destination. The format follows.
For photographs, start with JPG or WebP
Photos have many colors and gradual transitions. Lossy compression works well here because it can discard subtle detail without changing the overall impression much. JPG offers very broad compatibility. WebP often produces a smaller file at a similar visual quality, but the result depends on the picture and encoder.
Compare at the size people will actually see. A faint artifact visible at 400% zoom may not matter in a small website image; blocky edges on product lettering might.
For transparency, use PNG or WebP
JPG has no alpha channel. Transparent areas must be filled with a background color. If an image needs to sit over different backgrounds, choose PNG or WebP and inspect the edge against both light and dark surfaces.
For smaller photo downloads, also try AVIF
AVIF is another option for smaller photo downloads in the Ultra compressor. It supports transparency, but check the app or website receiving it. Encoding is slower and Luma currently supports AVIF only as a compressor output. Use JPG or WebP when compatibility is more important.
For text and sharp edges, test PNG
Screenshots, charts and flat artwork can expose the ringing and blur of lossy encoding. PNG preserves pixel values without that lossy step. It can be larger than a lossy image, especially for complex photos. Luma’s browser encoder does not offer a PNG quality setting or indexed palette optimization.
| Need | Start with | Check |
|---|---|---|
| Photo for a form or email | JPG | Dimensions and maximum attachment size |
| Transparent graphic | PNG or WebP | Edges and destination compatibility |
| Website photograph | WebP | Actual file size and visual quality |
| Screenshot with small text | PNG | Readability at the final size |
A conversion cannot recover missing detail
Saving a heavily compressed JPG as PNG prevents another lossy encode, but it does not remove existing compression artifacts. Converting an image repeatedly can add loss. Keep the original and make each new export from that original when possible.
Try it with your own image
Convert an image or compare compression settings. Check transparency and color as well as file size. Browser canvas processing can alter wide-gamut colors and does not retain the original color profile.