Written by Alex Chen — Frontend Engineer. building web apps for 10+ years. Built WebP2PNG when tired of converters that upload your files. More about me →
A client once asked me to convert 200 product photos from WebP to PNG "without losing any quality." Technically impossible — WebP is lossy, the artifacts are permanent. But visually? At high enough settings, nobody can tell. Here's what actually works, format pair by format pair.
Lossless conversion means every pixel in the output is identical to the input. This only works when both the source and destination formats support the same pixel data. Specifically:
The key phrase is "lossless mode." WebP has both lossy and lossless encoding — if you pick lossy, you're compressing, not just converting. That brings us to the tricky cases.
Some conversions inherently discard data. The most common trap: JPG → PNG. Converting a JPG to PNG won't restore the detail the JPG already threw away. The PNG will be 5-10x larger with zero quality gain. Don't do this unless you need transparency.
WebP (lossy) → PNG: The artifacts from WebP's lossy compression are baked in. Converting to PNG preserves them faithfully — it won't magically sharpen the image. Same rule: only convert if you need PNG-specific features.
Any format → JPG: JPG is always lossy. Even at quality 100%, the colorspace conversion from RGB to YCbCr introduces tiny rounding errors. For most practical purposes, quality 92-95% JPG is "visually lossless" — your eyes can't tell, even if the pixels technically differ.
Some converters re-compress images through a second lossy pass, degrading quality twice. This is surprisingly common in "free online converters" that upload your file to a server. A browser-local tool like WebP2PNG reads the original file directly and encodes the output once — no double-compression, no quality cascade.
| From → To | Lossless Possible? | Recommendation |
|---|---|---|
| PNG → WebP | Yes (use lossless mode) | 5-10x smaller, same pixels |
| JPG → PNG | No (damage is done) | Only for transparency needs |
| JPG → WebP | No (but 30% smaller at same visual quality) | Use quality 85%+ |
| WebP → PNG | Yes (if source was lossless WebP) | Safe for archiving |
| PNG → JPG | No (JPG is always lossy) | Use quality 92%+ for photos |
| JPG → JPG (re-save) | No (generation loss) | Avoid when possible |
Lossless conversion is real, but format-aware. Moving between lossless formats (PNG, lossless WebP, BMP) preserves every pixel. Converting to a lossy format (JPG, lossy WebP) means accepting some degradation — but at high quality settings, it's invisible. And never convert through two lossy steps when one will do.
Try it yourself: convert an image and download both formats to compare side by side.
Written by Alex Chen — Frontend Engineer. building web apps for 10+ years. Built WebP2PNG when tired of converters that upload your files. More about me →