Free tool · no signup · no upload
Compress PNG images — losslessly
Same pixels, smaller files. Unlimited lossless PNG optimization in your browser via OxiPNG — nothing gets uploaded.
Drop a PNG — smaller file, pixels identical. Captioned; no sound needed.
Drop images here or click to choose
PNG (or JPG/HEIC to convert) — as many as you like
🔒 Conversion happens entirely on your device via WebAssembly — files are never uploaded, stored, or seen by anyone. HEIC decoding uses libheif (LGPL).
Why unlimited and free?
PNG optimizers that meter you do the work on their servers. Here, OxiPNG — the open-source optimizer, compiled to WebAssembly — runs on your computer. No server costs, no credits, and your files stay private by construction.
Built by PrinterFlo, print shop management software. Also try: JPEG compressor · WebP & AVIF converter · HEIC to JPG
Frequently asked questions
Is the compression really lossless?
Yes. When you feed a PNG in and choose PNG out, the pixels are bit-for-bit identical — OxiPNG only optimizes how the file is packed (filtering, compression strategy, removing redundant metadata). Logos, screenshots and UI graphics typically shrink 10–40% with zero change in appearance.
Why is my PNG so big in the first place?
Most software saves PNGs quickly rather than optimally — default compression settings, embedded color profiles, and metadata all add weight. And if the PNG is a photograph, PNG is simply the wrong format: converting it to WebP or AVIF (also available here) can cut it 70–90%.
Does it keep transparency?
Fully. Lossless PNG optimization never touches the alpha channel, and converting to WebP or AVIF preserves transparency too.
Is there a limit on files or sizes?
No — the optimizer runs on your own machine via WebAssembly, so there's nothing for us to meter. Batch-drop your whole assets folder and download the results as a zip.
Are my images uploaded to a server?
Never. Everything happens locally in your browser; your files aren't transmitted, stored, or seen by anyone.
When should I convert PNG to WebP instead?
If the image is going on a website and doesn't need to stay PNG, WebP wins: it supports transparency and compresses far harder, especially for photos and screenshots. Keep PNG when a workflow specifically requires it (print handoffs, software that only accepts PNG, pixel-perfect archival).
More free tools: printerflo.com/tools