PNGQuant
Compress PNG files with pngquant, a command-line utility and library that preserves alpha transparency.
About PNGQuant
pngquant is a command-line utility and library for lossy compression of PNG images. It reduces file sizes, often by as much as 70%, while preserving full alpha transparency, with output stated as compatible with web browsers and operating systems.
It supports batch conversion, stdin/stdout chaining, custom output extensions, quality ranges, and speed settings. The code is available under the GPL or a commercial license, and the documentation suggests oxipng or ImageOptim for further size reduction.
Key features
- Lossy PNG compression that preserves full alpha transparency
- Batch conversion of multiple files, including recursive processing
- Stdin/stdout chaining for use in Unix-style pipelines
- Quality range setting from 0 to 100
- Speed setting from 1 to 10, default 3
- Custom output filename extension with --ext option
Best for: Developers and script or server-side users who process PNG files in bulk from the command line.
Good for
- Example reduction from 75,628 bytes to 19,996 bytes (73% smaller)
- Preserves full alpha transparency in compressed files
- Generated images are described as compatible with web browsers and operating systems
Watch out for
- Compression is lossy, so output differs from the original
- Files below the minimum --quality setting are not saved
- Documentation suggests using oxipng or ImageOptim for further reduction
PNGQuant at a glance
- Website
- pngquant.org
- Category
- Online Tools › Image Tools
- Type
- Online tool
- Pricing
- Not confirmed. Check the site
- Platforms
- Linux, macOS, Web, Windows
- Open source
- Not stated
- Last checked
- Oct 5, 2026 · Online when checked
- Listed
- Oct 5, 2026
Guides for Image Tools
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PNGQuant FAQ
How much can pngquant reduce PNG file size?
Often as much as 70%. The example shows a reduction from 75,628 bytes to 19,996 bytes, or 73% smaller.
What happens if an image does not meet the minimum quality setting?
The image won't be saved. When outputting to stdout, the 24-bit original is output instead, and pngquant exits with status code 99.
How do I convert multiple files at once?
Use batch conversion, for example: pngquant 256 *.png.
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