Conversion guide
PNG to WebP: when it shrinks, when it backfires
When PNG to WebP conversion pays off, when it grows files, and how transparency, screenshots, and photos each change the answer.
Converting PNG to WebP is one of the most reliable ways to cut image weight on the web - and one of the easiest to do badly. The savings depend entirely on what is inside the PNG. Some files shrink by 80%. Some barely move. A few get larger.
This guide covers when the conversion pays off, when it backfires, and how to check before you ship anything.
What actually changes
PNG is a lossless format: every pixel survives exactly. WebP offers two modes - lossless, which also preserves pixels, and lossy, which discards detail the eye is unlikely to notice in exchange for much smaller files.
That gives you three realistic outcomes when converting:
- PNG → lossy WebP usually produces the big savings, at the cost of exact pixel fidelity.
- PNG → lossless WebP keeps every pixel and still beats PNG on size for most images, though by a smaller margin.
- PNG → WebP on an already-tiny file can go either way, including slightly up.
When it shrinks
- Photographic content stored as PNG. This is the jackpot case. Screenshots that include photos, exported design mockups, and camera images someone saved as PNG carry enormous overhead, because PNG has no good way to compress photographic gradients. Lossy WebP routinely cuts these by 60-90%.
- Screenshots of interfaces. Lossless WebP typically beats PNG here while keeping text pixel-sharp. Lossy WebP saves more but can smudge fine text at aggressive settings - compare at 100% zoom before deciding.
- Images with transparency. WebP supports full alpha in both modes, so transparency is not a reason to stay on PNG. Lossy WebP with alpha is usually far smaller than the equivalent PNG.
- Large illustrations and gradients. Smooth gradients that force PNG into large files compress well in WebP.
When it backfires
- Small flat-color graphics. A well-optimized 3 KB palette PNG (an icon, a simple logo) is already near its floor. WebP may only match it, and the conversion overhead can push the result slightly above the original.
- Pixel art and hard-edged graphics through lossy WebP. The lossy encoder is tuned for natural images; hard edges can ring or blur. Use lossless mode for this content, or keep the PNG.
- Anything that goes back the other way. Converting WebP to PNG almost always grows the file - sometimes several times over - because PNG must store losslessly what WebP stored lossily. Do it when a tool demands PNG input, not for delivery.
A note on how our tools report this: compression on Tinify.dev never
returns a file larger than the input - when nothing can be saved, you
get the original back marked optimized: false. Conversion is different.
Changing formats can legitimately increase size, and the result reports
the byte change plainly either way, so check the numbers before replacing
files.
Transparency, in slightly more detail
PNG's alpha channel is the main reason it survived this long on the web. WebP handles the same use cases: 8-bit alpha in both lossless and lossy modes. Two practical cautions:
- In lossy mode, semi-transparent edges (drop shadows, anti-aliased cutouts) are where artifacts appear first. Inspect edges against both light and dark backgrounds.
- Some older non-browser software still cannot open WebP. If a file also needs to work in email clients or legacy tools, keep a PNG copy.
Screenshots vs photos: a quick decision table
| Content | Recommended conversion | Why |
|---|---|---|
| Photo saved as PNG | Lossy WebP | Largest savings, invisible loss |
| UI screenshot with fine text | Lossless WebP | Smaller than PNG, text stays sharp |
| Icon or logo under ~10 KB | Usually keep PNG | Little to gain, occasionally negative |
| Graphic with transparency | WebP (mode by content) | Full alpha support, smaller files |
| Pixel art | Lossless WebP or PNG | Lossy encoding softens hard edges |
How to convert without regrets
- Convert a copy with the PNG to WebP tool - free, no account, up to 50 files of 40 MB each, deleted after two hours.
- Compare the byte counts. If the WebP is not meaningfully smaller, keep the PNG.
- Inspect text, edges, and transparent regions at 100% zoom.
- Keep the original PNG as your master file. Formats will change again; re-encoding a lossy file compounds the loss.
If the PNG is staying a PNG - because it is small, or because a consumer requires it - it is still worth a pass through the PNG compressor, which reduces palette and metadata overhead without changing the format.
For choosing between WebP, AVIF, JPEG, and PNG more broadly, see our format guide. The short version for this pair: if the image came from a camera, it should probably not be a PNG at all; if it came from a screen, WebP usually wins but measure first.