IMAGE TOOLBOX / GUIDE
PNG vs JPG vs WebP: Which Image Format Should You Use?
How the three formats differ, with measured file sizes instead of rules of thumb.
The three formats compress in fundamentally different ways
PNG is lossless. It keeps every pixel exactly as it was and only reorganizes the data more efficiently, so quality never drops. The price is size: photos, with their endless color variation, come out large.
JPG is lossy. It throws away detail that the human eye barely notices, which shrinks photos dramatically. It struggles with flat colors and sharp edges, though, which is why screenshots and UI graphics often look worse or even get larger as JPG.
WebP is newer and supports both lossy and lossless modes. This site's compressor outputs lossy WebP, which often matches JPG's visual quality at a smaller size.
Transparency and compatibility
If you need a transparent background, choose PNG or WebP; JPG has no alpha channel. WebP works in every modern browser, but older desktop software and some photo editors still cannot open it. When compatibility matters more than size (a file you are sending to someone with unknown software), PNG or JPG is the safer choice.
What we measured
Theory only goes so far, so we compressed two test images (one photo-like, one flat graphic) with this site's own compressor and recorded the exact byte counts. The full table is on the benchmark page (in Korean, but the numbers are universal). These figures come from the browser's built-in JPG encoder; JPG output on this site now uses MozJPEG, which produces a smaller file at the same quality value (on a synthetic 1600×1200 photo at quality 75 we measured 287,186 bytes with the browser encoder and 180,789 with MozJPEG; other images will differ). The short version:
On the photo-like image, both JPG and WebP at 80% quality cut the file by more than 90%: from 1,808,456 bytes to 115,393 (JPG, 93.6% smaller) and 123,720 (WebP, 93.2% smaller). On the flat graphic, JPG at 100% quality came out bigger than the original PNG (35,171 vs 22,791 bytes), while WebP at 100% was 73.6% smaller (6,010 bytes).
Which one should you pick?
Photos: JPG or WebP at around 80% quality.
Logos and graphics that need a transparent background: PNG (guaranteed lossless) or WebP.
Screenshots and UI with lots of flat color: WebP, or PNG if compatibility is a worry.
This comparison covers still images only (JPG, PNG, WebP). The compressor also saves AVIF and accepts iPhone HEIC photos, but it does not handle animated GIFs. AVIF is not always smaller than JPG and takes longer to encode, so it was left out of the measurements.
FAQ
Why can't some programs open WebP files?
WebP is relatively new, so older image editors and a few default OS viewers do not support it. Every modern web browser does.
Does converting PNG to JPG always make the file smaller?
Usually, but not always. Images with flat colors and sharp edges can get larger as JPG. See the measured numbers above.
I want to shrink a file with zero quality loss. What should I do?
Keep PNG and set "PNG colors" to Original for true lossless output. The quality slider does not shrink a lossless PNG, so to make it smaller either reduce the pixel dimensions or use the color-reduction option (256 colors by default), which cuts screenshots and graphics a lot but can show slight banding in photos.
Does re-saving an image over and over make it worse?
Yes for JPG and lossy WebP: every save discards a little more detail. If you need several versions, always compress from the original file. PNG does not suffer from this.
Can I convert several photos at once?
Yes. You can select up to 10 images at a time and download the results as a single ZIP. Selecting one image keeps the single-image flow.