Yes: a lossless WebP keeps every pixel of a PNG and is usually about a quarter smaller. On 52 PNGs from the Heart Photos wall, lossless WebP was smaller than a carefully saved PNG every time, by 28% at the median, and each one decoded back to exactly the same pixels. Keep PNG where an app or a person needs that format, or where you need 16 bits per channel; use WebP to serve those images on the web.
Is WebP lossless or lossy?
Both, and that is the source of most confusion. WebP has two modes:
- Lossless WebP stores every pixel exactly, like PNG. It is the mode to compare with PNG.
- Lossy WebP throws away detail the eye is unlikely to miss, like JPEG. It is much smaller, but the pixels are not the same.
Many converters use lossy mode unless you ask for lossless. With Google's own tool, cwebp, the default is lossy at quality 75, and its documentation lists -lossless as the switch to "encode the image without any loss." So if a converted file is far smaller than the PNG, check which mode made it.
How much smaller is lossless WebP than PNG?
Google says lossless WebP images are 26% smaller than PNGs, and MDN gives the same figure. Google's lossless study (last updated Aug 1, 2017) ran 12,000 PNGs from the web against PNGs already squeezed by pngcrush and ZopfliPNG, and found WebP denser on more than 99% of them.
We checked that on images of our own. On Nov 4, 2026 we took the 52 PNG originals in the wall's Made by AI tag that are not photographs of people: landscapes, interiors, logos, game screenshots, from 0.6 to 4.2 megapixels (1.5 by median), one with transparency. For each one we made:
- a PNG saved again by Pillow with
optimize=True, so the PNG is not losing because it was carelessly saved, - a lossless WebP with libwebp 1.6.0:
cwebp -lossless -z 9 -exact, - a lossless JPEG XL with libjxl 0.12.0:
cjxl -d 0 -e 7, for comparison, - a lossy WebP at
cwebp -q 80, to show the size of the other mode.
Then we decoded every lossless file back to pixels and compared it with the PNG, pixel by pixel.
| Median size vs the optimized PNG | Range across the 52 | All 52 together | Same pixels | |
|---|---|---|---|---|
| PNG, optimized | 100% | 100% | 112.5 MB | Yes |
| WebP, lossless | 72% | 57% to 81% | 77.6 MB | Yes, all 52 |
| JPEG XL, lossless | 66% | 49% to 79% | 70.5 MB | Yes, all 52 |
| WebP, lossy (q 80) | 7.5% | 1% to 14% | 10.7 MB | No |
So the published figure held up: a 28% saving by median here against Google's 26%, and WebP never lost to PNG. Lossless JPEG XL was smaller still, by about 9% against the WebP, on all 52.
Two honest caveats. These are one wall's images, many of them made by AI, not a scientific test set. And -z 9 is libwebp's slowest setting: it took a median of 11 seconds per image on our PC with four images encoding at once. The default lossless setting is much quicker and gives up a little size.
Does converting PNG to WebP lose quality?
Not in lossless mode. Every one of our 52 lossless WebPs decoded to exactly the pixels of its PNG, transparency included.
What can be lost is not pixels but extras:
- Bit depth. MDN notes that lossless WebP uses 8 bits per channel, while PNG can hold 16. A 16-bit PNG (common from scanners, HDR work and some editors) loses precision in WebP.
- Colors under transparent pixels. By default
cwebpmay change the color of fully transparent pixels to compress better;-exactkeeps them. It does not change what you see, but it matters if a program later reads those values. - Metadata. Text chunks, color profiles and creation times can be dropped by a converter. Check yours if they matter.
- Size. WebP images can be at most 16,383 by 16,383 pixels; PNG's limit is far larger.
Which should you use?
| If you want to | Use |
|---|---|
| Serve screenshots, logos or graphics on a web page | WebP, lossless for sharp text and edges |
| Serve a photo on a web page | Lossy WebP or AVIF, not PNG |
| Keep an exact master copy | PNG, or lossless JPEG XL if your tools read it |
| Keep 16 bits per channel | PNG |
| Send a file to someone whose software you do not know | PNG |
| Upload to a site that refuses WebP | PNG |
Browser support is no longer the worry it was: Can I use showed 97.18% of browsers supporting WebP on Nov 4, 2026, with Safari in full since version 16. Older desktop software, some print services and a few upload forms are where WebP still gets turned away.
How do you convert PNG to WebP without losing quality?
With Google's free command-line tool, from the WebP downloads page:
cwebp -lossless -exact photo.png -o photo.webp
Add -z 9 for the smallest file if you can wait, or leave it off for speed. To turn a WebP back into a PNG, dwebp photo.webp -o photo.png does it. If you use an app or a website instead, look for a setting called "lossless" and make sure it is on; a quality slider usually means lossy.
Frequently asked questions
Is WebP better than PNG?
For showing images on the web, usually yes: the same pixels in a smaller file, in almost every browser. For keeping or exchanging files, PNG is still the safer choice because more software reads it and it can hold 16 bits per channel.
Why is my WebP bigger than the PNG?
It is rare in lossless mode: Google's study found WebP smaller on more than 99% of 12,000 web PNGs, and in our 52 it never lost. When it does happen, try a higher effort setting (-z 9), and if the WebP is still bigger, keep the PNG.
Does WebP support transparency?
Yes, in both modes. Google says transparency costs lossless WebP about 22% more bytes, and that lossy WebP with transparency is typically three times smaller than the PNG.
Should I convert all my PNGs to WebP?
For a website, converting the copies you serve is worth it. For your own archive, keep the PNG originals (or store them losslessly in a way you can turn back into the same pixels), so nothing depends on one format.
What Heart Photos does
Heart Photos does this for you, and checks it. When you upload a PNG, it makes both a lossless JPEG XL and a lossless WebP of it, keeps whichever is smaller, and keeps it only after decoding it and finding exactly the same pixels; otherwise your PNG stays as it was. On the 67 PNGs in the wall's Made by AI tag on Nov 4, 2026, the stored file was 40% smaller than the upload by median, and not one pixel different. Download Original and you get a PNG of exactly those pixels, with its color profile. What visitors see is served as AVIF, in the sizes each screen needs.
To try it on your own images, Open Heart Photos and upload a PNG. For the formats side by side, read AVIF vs JPEG XL vs WebP, and before you share a screenshot or photo, how to remove location data from it.