PNG Compressor
Compress PNG files using colour quantisation. No upload, transparency preserved.
🖼️
Drop PNG files here or
PNG files only. Files never leave your browser.
PNG Compressor is a browser-based tool that reduces PNG file size through colour quantisation — the same technique used by dedicated tools like pngquant. Rather than re-encoding at a lower visual quality in the traditional sense, it reduces the number of unique colours in the image, which shrinks the palette and significantly decreases file size. Transparency is always preserved throughout the process.
Tool interface
The interface is structured for ease of use:
- A drag-and-drop upload area for one or multiple PNG files
- A quality slider that controls the colour palette size
- A file list showing each filename and its original size
- Live size comparison after compression (original → compressed, savings %)
- A
Compress & Downloadbutton to process and save all files - A
Clearoption to reset and start over
For multiple files, the output is packaged into a single ZIP archive.
Tool description
PNG Compressor uses the UPNG library to perform colour quantisation on PNG images. The quality slider controls the colour palette size — lower values use fewer colours, producing smaller files at slightly reduced colour accuracy. Higher values preserve more colours and image fidelity.
Unlike JPEG compression, this process preserves transparency (alpha channel) completely. The tool is especially effective on images with large uniform areas, limited colour ranges, or transparent backgrounds — typical of logos, icons, interface screenshots, and line art.
If quantisation does not reduce the file size, the tool falls back to lossless PNG re-encoding. If even the lossless version is larger than the original, the original file is returned unchanged with an "already optimized" notice.
Some practical use cases:
- Compressing logo files for web use while keeping transparency
- Shrinking screenshots and UI mockups for documentation
- Reducing file sizes of icon sets and sprite sheets
- Preparing diagrams and charts for embedding in reports
- Batch-compressing PNG exports before uploading to a website
How to use
- Drop PNG files onto the upload area, or click
Browseto select them. - Adjust the quality slider — around 80% preserves good colour fidelity while still reducing size noticeably.
- Click
Compress & Downloadto process the files. - Review the size comparison shown next to each file name.
- Single files download directly; multiple files are packaged as a ZIP archive.
Tip: PNGs with photos or complex gradients gain less from palette reduction. This tool works best on graphics, logos, and illustrations with a limited range of colours.
FAQ
Only PNG files are accepted?
Yes. This tool is specifically for PNG images. For JPEG or WEBP use the dedicated JPG Compressor or WEBP Compressor.
How does the quality slider affect PNGs?
The quality slider controls the number of colours kept in the quantised image. Lower values shrink the palette more aggressively. PNG compression here is about colour reduction, not lossy re-encoding like JPEG.
Will transparent areas be affected?
No. Transparency is fully preserved. The alpha channel is kept intact through the quantisation and re-encoding process.
Can I compress multiple PNG files at once?
Yes. Drop or select multiple files and they will all be processed together, with the compressed output saved as a ZIP archive.
Are my images uploaded anywhere?
No. Everything runs locally in your browser. Your files are never sent to a server.
Why does it say "already optimized"?
Some PNGs are already in a near-optimal state. When neither quantisation nor lossless re-encoding can make the file smaller, the tool returns the original unchanged.