Features

PNG optimizer

Losslessly re-encode PNG files to strip metadata and pick the smallest DEFLATE pass — typically 15–40 % size reduction with no pixel change.

What it does

The PNG Optimizer rewrites a .png file using a smarter encoder than most image software uses by default. The pixel data after decoding is byte-for-byte identical to the source — this is lossless optimisation, not compression at the cost of quality.

Three steps run automatically:

Metadata strip — EXIF, ICC profile, XMP, and other ancillary chunks are removed unless you opt to keep them. Most web use cases do not need any of these.
Filter search — PNG supports five per-row predictor filters (None, Sub, Up, Average, Paeth). The default encoder in browsers and Photoshop picks one heuristically; the optimizer tries combinations and picks the smallest result per scan line.
DEFLATE re-pack — the raw zlib stream is replaced with a tighter compression pass using zlib.deflate at level 9 with a tuned window.

Typical savings: 15–30 % on screenshots, 20–40 % on UI mockups, 5–15 % on photographic PNGs (which usually compress better as WebP or AVIF anyway).

When to use it

Final pass on PNG artwork going into a website or app bundle.
Anywhere you need a real PNG (transparency + universal compatibility) and want it as small as possible.
Cleaning up screenshots from a screen-capture tool before sharing.

When NOT to use it

If you can switch to WebP or AVIF — those are a different story. WebP-lossless is typically 25–35 % smaller than even an optimised PNG. Use the Format Converter for that.
For photographic content. The savings on photo PNGs are modest; converting to a lossy format gives much bigger wins.

Preserving colour profiles

If your PNG has an embedded ICC profile that downstream tools rely on (print workflows, colour-managed displays), tick "Keep ICC profile" before optimising. The saving is smaller but colour accuracy is preserved exactly.

By default the ICC profile is stripped because most web pipelines do not honour it and the bytes are wasted.

Batch optimisation

Drop a folder of PNG files; each is processed independently. Comparison output shows original size, new size, and percentage saved per file.

Privacy

All processing runs in your browser via a WebAssembly DEFLATE encoder (zlib-ng compiled to WASM). No file is ever uploaded.

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