Convert PNG to WebP — Lossless for UI, Lossy for Photos, Decided Per File
The one-pass fix for a mixed PNG folder. Screenshots go lossless. Photos go lossy-with-alpha. One drop zone, one batch, one ZIP out — nothing uploaded.
A router, not a slider
Drop your PNGs — mixed or otherwise. Every file gets the path that makes it smaller at the quality bar. You don't pick. You don't sort. You get a ZIP back.
Supported input formats
- ✓ JPG / JPEG — Photos, portraits, web content
- ✓ PNG — Screenshots, icons, transparent images
- ✓ HEIC / HEIF — iPhone photos, Apple formats
- ✓ TIFF — Scans, prints, high-resolution archives
- ✓ GIF — Animations and static GIFs
- ✓ BMP, PSD & more — Anything ImageMagick can decode
How the conversion works
- 1. DropDrag files or a whole folder into the box below. Folder structure is preserved in the output ZIP.
- 2. AnalyzeEach image is analyzed for entropy and content type. The engine picks per-image quality settings targeting PSNR ≥ 44.5 and SSIM ≥ 0.95.
- 3. EncodeConversion runs on all of your CPU cores in parallel via Web Workers. EXIF, ICC color profiles and geolocation are copied onto the WebP or AVIF output.
- 4. DownloadWhen the batch is done, a ZIP containing every converted file downloads automatically. No re-upload, no waiting on a server.
Why WebP is the right target for a PNG archive
PNG is two formats sharing one file extension: a lossless codec for synthetic graphics, and a last-resort container that people accidentally export photos into. WebP has a clean answer for each case, so you don't have to sort.
PNG is two formats sharing one extension
Open any real PNG folder and you'll find two different things cohabiting. One pile is synthetic — screenshots, UI mockups, logos, diagrams, flat icons — where PNG was genuinely doing useful work. The other pile is photographs someone exported as PNG by mistake, sitting there at 15 MB each, taunting your disk. Most tools ask you to sort them. This one doesn't.
A router, not a slider
Each file gets inspected. If it's flat and synthetic, it goes through the lossless path and lands 20–30% under the source with every pixel intact. If it's photographic, it takes the lossy-with-alpha route and drops 70–90% of the weight without a visible artefact. The decision is per-file and automatic. You don't pre-sort. You don't pick an encoder. You drop the folder.
Alpha is a first-class channel
Both paths carry the alpha plane end-to-end. The feathered edge on a cut-out logo, the gradient under a drop shadow, the 40% overlay in a product mockup — they survive. If the source turns out to be fully opaque (a surprising number of 'transparent' PNGs are), the alpha plane gets dropped and the output shrinks a little more.
What survives the trip
Your Photoshop export with a Display P3 profile still looks right on a calibrated monitor. ICC, EXIF and XMP are lifted during decode and rewritten onto the WebP. DPI hints carry across where WebP has a matching field; anything it can't represent gets dropped honestly rather than faked.
What actually changes when you re-encode
| Criterion | PNG | WebP |
|---|---|---|
| UI screenshot / flat graphic | baseline | ~20–30% smaller (lossless) |
| Photo-ish PNG (24-bit gradients) | baseline | 70–90% smaller (lossy + alpha) |
| Transparent pixel handling | 8-bit alpha | 8-bit alpha, full fidelity |
| Encoder path chosen | DEFLATE, always | Lossless or lossy-with-alpha, per file |
| Metadata (ICC / EXIF / XMP) | stored in PNG chunks | copied to output |
| Browser support | universal | universal (Safari 14+, all others) |
| Animated input (APNG) | rare native support | first frame only |
How SciZone converts PNG to WebP
Drop the folder, let the per-image router pick the path, download the ZIP.
- 1
Drop the whole archive
Drag a folder of PNGs — mixed screenshots, logos, Figma exports, stray photo-PNGs — onto the drop zone. Nested folders come out of the other side intact. A 48 MP surprise hidden in the pile won't blow the heap on arrival.
- 2
Per-image routing runs
Each file is inspected — entropy, resolution, whether the alpha channel is doing anything non-trivial. The encoder picks the path that'll produce the smaller file at the quality bar. No slider. No dropdown. No decision fatigue.
- 3
Quality picked per image, where it applies
Photos get an adaptive quality search — a short look for the setting that's transparent to the eye on that specific image. Lossless paths skip the search entirely and just write the compressed bitstream.
- 4
Grab the ZIP
Your WebPs come out as a ZIP mirroring the input folder structure. The results page shows the lossless-vs-lossy decision and per-file byte savings so you can spot-check anything that looks surprising.
WebP Results
See how WebP compresses real photos with our Excellent preset — the default when you click convert.
Typical WebP savings
Measured on 24 diverse photos at matched perceived quality (SSIM ≥ 0.95)
PNG to WebP — questions teams actually ask
I have screenshots and product photos saved as PNG in the same folder — does that matter?
That's exactly the intended workload. Each file is routed independently, so a screenshot can come out as lossless WebP in the same batch that turns a photo-PNG into lossy WebP with alpha. Don't pre-sort. It'll figure it out.
How is this different from dragging PNGs into Squoosh one at a time?
Squoosh asks you to pick an encoder and a quality number for every file. This tool picks both automatically using a perceptual-quality target, and runs the batch across every core you have. On a 500-screenshot archive the human-time difference is hours, not minutes.
What does 'lossless WebP' actually save versus the source PNG?
About 20–30% on typical UI captures, sometimes more on logos and icons. Both files are pixel-for-pixel identical. If lossless happens to be bigger on a particular input (rare, but possible), the engine falls back to the lossy path automatically.
Why is there a small download the first time?
That's the WebAssembly image engine — under 5 MB to download, once. After that it's cached; subsequent visits and extra batches don't re-fetch.
Does it matter if my PNG has no transparency at all?
A tiny bit, yes. If the alpha channel is uniformly 255, the encoder drops the plane entirely and the output is a plain three-channel WebP — usually a few percent smaller than carrying an unused alpha along for the ride.
Do the workers get recycled during a long batch?
Every worker is retired after 32 jobs and a fresh one takes its place. That's what keeps a 1000-file batch from quietly leaking memory — without the recycle we saw growth past a gigabyte on long runs, the kind of thing you only notice once the tab crashes.
Can I force everything to lossless mode?
Not from the UI today. The per-image router is the defining feature of the tool — overriding it would make the output worse on photo-PNGs, which defeats the purpose. If you need bitwise-identical lossless output on a photo archive, re-encoding to WebP at all is the wrong step. Keep the source.
Does anything get uploaded?
No. Every encode happens inside the tab. Open DevTools → Network during a run and you'll see the engine load once and nothing else leave. The cross-origin isolation you may notice in the console is there so the encoder can thread across your cores, not for any remote call.
Why Choose SciZone?
We're not just another optimizer. We engineered a fundamentally better solution.
| Feature | SciZone (You're here) | Other Optimizers |
|---|---|---|
| CPU Utilization
How processing power is used
| True Multi-Threading Intelligently uses all CPU cores without overloading your system | Single-Threaded Uses only one CPU core, wastes available power |
| AVIF Encode Speed
How fast AVIF actually runs in the browser
| Tile-Parallel Encoding Each AVIF image is split into tiles encoded across every core — ~6× faster than single-tile libaom on large photos | Single-Tile Default libaom's internal threading caps around 4 threads per encode, regardless of how many cores you have |
| Quality Settings
How compression is optimized
| Unique Per Image Algorithm analyzes each photo and picks optimal settings | One-Size-Fits-All Same settings for every photo, inconsistent quality |
|
Metadata & Color Profiles
Preservation of image data
| Fully Preserved EXIF, color profiles, geolocation. Everything stays intact | Often Stripped Color profiles lost, metadata incomplete |
|
Quality-Size Balance
Optimization results | Perfect Balance Maximum compression with imperceptible quality loss | Inconsistent Either too large or noticeable quality loss |
The Bottom Line
Every photo is unique. Our intelligent algorithm understands this and analyzes each image individually to find the perfect balance between file size and quality. We utilize your computer's full power without overloading it, preserving every detail of your metadata and color profiles. Your files are smaller, faster, and absolutely perfect. 🎯