Compress PNG Images Online for Free

Processing securely on your device, no data sent to any server

or drop files here

Lossy colour quantisation trims a PNG down to a 256-colour palette. Up to 80% smaller. Nothing uploaded.

How it works

Three steps. Done in your browser.

Drop your PNG

Drag a PNG file onto the zone or click to browse. No file size limit. Transparency is preserved throughout.

Set the quality level

UPNG.js runs in your browser as plain JavaScript. Higher quality preserves more colour depth with a larger file.

Save your smaller PNG

Typically 40-80% smaller than the original. Transparency preserved. Nothing sent to any server at any point.

Why it matters

Where a smaller PNG makes the biggest impact.

PNG files are losslessly compressed by default, meaning they preserve every pixel exactly. That makes them large. Lossy palette quantisation fixes that without changing the format or losing transparency.

Website performance

Large PNGs are one of the most common causes of poor Lighthouse scores. Compressing logos, icons, and screenshots before uploading to a CMS reduces page weight and improves load times.

App and game assets

Sprite sheets, UI textures, and icon atlases must be compact to minimise bundle size and reduce memory usage on mobile devices. Compressed PNGs load faster and use less RAM.

Logos and branding assets

Brand logos sent over email or embedded in documents are often oversized PNGs. A compressed logo under 100 KB looks identical but loads instantly and reduces document file size.

Screenshots and documentation

Screenshots saved as PNG are often several megabytes. Compressing before embedding into presentations, wikis, or PDFs significantly reduces the final document size.

Email signatures and templates

Large embedded PNGs cause emails to load slowly or get flagged by spam filters. A compressed PNG logo under 50 KB renders instantly in every email client.

Cloud storage and backups

Archiving large volumes of screenshots or design exports? Compression can cut storage footprint by 50-80% with no visible quality loss on screen.

How PNG compression works under the hood.

Unlike most online tools that upload your file to a remote server, this compressor runs entirely in your browser tab. It loads UPNG.js, an open-source JavaScript PNG encoder. UPNG.js builds a K-d tree over the pixels to find a palette of at most 256 colours for each image, then re-deflates the indexed data, minimising visible quality loss while dramatically reducing file size.

Alpha-channel transparency is fully preserved throughout the process. Your file never leaves your device. There is no server, no upload, and closing the tab immediately clears all image data from browser memory.

Common questions

Questions answered.

How does PNG compression work?

This tool uses UPNG.js, an open-source lossy PNG compressor written in JavaScript. It reduces the number of colours from 16.7 million (24-bit) down to a palette of at most 256 (8-bit) using K-d tree quantisation, then re-deflates the result. The output is a smaller file that looks nearly identical at normal viewing sizes.

Will lossy compression ruin my PNG?

At quality settings above 70, the visual difference is virtually imperceptible on screen. At lower settings you may notice slight banding in gradients or flat colour areas. The quality slider lets you find the right balance for your use case.

Should I compress PNG or convert to JPEG?

If your image has transparency or is a logo, icon, or flat-colour graphic, compress the PNG. If your image is a photograph without transparency, converting to JPEG or WebP will give a much smaller file than any PNG compressor can achieve.

Is my PNG uploaded to a server?

No. The compression runs in your browser as JavaScript, on your own CPU. Your PNG file never leaves your device, not even temporarily.

Can I compress multiple PNGs at once?

Yes, up to 20 files at a time. All processing runs locally in your browser.

Does compressing a PNG preserve transparency?

Yes. The quantiser works on the full RGBA data, so alpha-channel transparency is preserved. Logos and icons with transparent backgrounds will retain their transparency after compression.

How much file size reduction should I expect?

Typical reduction is 40-80% depending on the image content. Flat-colour graphics and logos compress better than photographs. Photos with complex colour gradients compress less because the palette reduction is more visible.

What is the difference between compressing PNG and converting to WebP?

Compressing the PNG keeps it as a PNG, useful when you need PNG format for compatibility or transparency. Converting to WebP typically achieves an additional 25-50% size reduction on top of PNG palette compression, at the cost of changing the format.

Related tools

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