“Convert it to PNG for better quality” is one of the most repeated and least accurate pieces of advice about images. We converted two photos, a screenshot and a transparent app icon between JPG, PNG and WebP, using the browser encoders and the real converter pages on this site, and recorded the file sizes and what happened to transparency. The headline: the format is a choice about what is in the picture and where it will be used, and converting never adds quality that is not already there.
What each format is good at
- JPG is lossy and built for photographs: it throws away detail your eye is least likely to miss to get small files. It cannot store transparency. Everything opens it.
- PNG is lossless: every pixel is kept exactly. That makes it right for logos, screenshots, text and anything with transparency, and wasteful for photos. It supports transparency.
- WebP can be lossy or lossless and supports transparency in both modes. It is designed for the web and is the smallest of the three in most of our tests. Browsers support it very widely, but not every program or upload form does.
The same pictures in every format
We saved each image in every format with the browser's encoder. The photos are the 1024 × 1024 sample photos our tools ship with, and the screenshot is a 2560 × 1560 capture of our EMI calculator.
| Image | Original | PNG | JPG 90% | JPG 80% | WebP 90% | WebP 80% | WebP lossless |
|---|---|---|---|---|---|---|---|
| Portrait photo | 687 KB (JPG) | 2,006 | 186 | 119 | 136 | 76 | 1,038 |
| Product photo | 596 KB (JPG) | 1,727 | 138 | 84 | 89 | 51 | 892 |
| UI screenshot | 242 KB (PNG) | 373 | 276 | 207 | 149 | 107 | 453 |
All figures except the original are in KB. A few things stand out:
- PNG is the wrong container for a photo. It stored the portrait in 2,006 KB, more than ten times the 186 KB of a JPG at 90%.
- Lossless WebP roughly halved the photo PNGs (1,038 KB against 2,006 KB), so if you need a lossless photo, WebP lossless is much more efficient than PNG.
- For the screenshot, lossless WebP was larger than PNG (453 KB against 373 KB) in Chrome's encoder. Do not assume WebP always wins; for flat graphics test both.
- The browser's PNG is not the smallest possible PNG. Our original screenshot file was 242 KB, and passing it through the browser's encoder made it 373 KB. Converting a PNG to a PNG in a browser can make it bigger.
Why JPG to PNG never improves a picture
When you convert a JPG to PNG, the PNG stores the JPG's decoded pixels exactly, including every compression artefact. Nothing is recovered, because the detail was thrown away when the JPG was first saved. In our test the PNG from the portrait was 2,006 KB against 687 KB for the JPG, and a check of the pixels showed them identical.
Going back again does not cost much extra either. We converted each photo from JPG to PNG and back to JPG at 90%: the result was 186 KB at a quality score of 41.5 dB for the portrait, exactly what saving the original straight to JPG at 90% gives. The detour only costs you the 2 MB middle step. Convert to PNG when a program needs it, such as an editor that works on layers, not as a way to improve quality.
What happens to transparency
We ran our transparent app icon through the real converter pages on this site and checked the result's corner, which was fully transparent in the original.
| Conversion | Result size | Corner of the result | Transparency kept? |
|---|---|---|---|
| Original PNG | 9.1 KB | Transparent | – |
| PNG to JPG, flatten to white | 11.3 KB (+24%) | White | No |
| PNG to JPG, flatten to black | 11.1 KB (+22%) | Black | No |
| PNG to WebP | 6.5 KB (−29%) | Transparent | Yes |
JPG has no way to store transparency, so any converter must pick a background colour to fill it with, and the PNG to JPG tool lets you choose white, black, light grey or your own colour. Once you save the JPG, the transparent area is gone for good. Keep your PNG. The small icon also got larger as a JPG, because JPG is poor at sharp edges and flat colour; the same file as a lossy WebP with transparency was almost a third smaller.
WebP: when it wins, and when it does not
In our image compression tests, WebP was 29% smaller than JPG for the portrait, 45% smaller for the product photo and 62% smaller for the UI screenshot at the same quality score. For pictures that stay on web pages that is free bandwidth.
It is also widely supported. According to caniuse.com, about 97% of users worldwide were on a browser that supports WebP (StatCounter, September 2026), with full support from Chrome 32, Edge 18, Firefox 65 and Safari 16. The remaining gap is mostly outside the browser: some online forms refuse WebP uploads, older desktop programs cannot open it, and print shops usually want JPG or PNG. If you are sending a file to a person or an upload box you do not control, convert to JPG.
Which format to choose
| You have… | Use | Why |
|---|---|---|
| A photo for a web page | WebP (or JPG) | Smallest at the same look |
| A photo to email, upload to a form or print | JPG | Opens everywhere |
| A logo or icon with transparency | PNG or WebP | JPG cannot keep transparency |
| A screenshot or text-heavy graphic | WebP (lossy) or PNG | JPG smears sharp edges and was biggest in our test |
| A cutout from the background remover | PNG, or WebP for the web | Needs the transparent area |
| An image to edit again later | PNG or the original | No further quality loss on each save |
How to convert, step by step
- Open the Image Converter and choose JPG, PNG or WebP as the output. For the two most common jobs there are dedicated pages: PNG to JPG and JPG to PNG, which can also make a white background transparent.
- Add your file. Nothing is uploaded; conversion happens in your browser.
- Set the quality (the PNG to JPG tool starts at 85%) and, for PNG to JPG, choose the background colour that replaces transparency.
- Download the result and compare the size shown with the original. If the new file is larger, you picked the wrong format for that image.
- To shrink it further, use the Image Compressor or reduce the dimensions with the Image Resizer.
What we did not test
We did not test AVIF or HEIC, animated GIFs or WebP animations, or colour-profile handling. Other encoders (and other browsers) will give different sizes, and two photos and one screenshot are a small sample, so use the numbers to see the pattern, not to predict your exact file.
