pngcrush

Optimize PNG files for smaller size

TLDR

Optimize PNG

$ pngcrush [input.png] [output.png]

Optimize in place

$ pngcrush -ow [image.png]

Remove metadata

$ pngcrush -rem alla [input.png] [output.png]

Best compression

$ pngcrush -brute [input.png] [output.png]

Reduce colors

$ pngcrush -reduce [input.png] [output.png]

Batch optimize all PNGs in a directory

$ pngcrush -d [output_dir/] [input_dir/]*.png

Set specific compression level (0-9)

$ pngcrush -l [9] [input.png] [output.png]

SYNOPSIS

pngcrush [options] input [output]

pngcrush optimizes PNG files by testing multiple compression strategies and selecting the smallest result. The optimization is completely lossless - the image data is preserved exactly while reducing file size through better compression parameters.The -brute option tries all filter and compression combinations for maximum reduction at the cost of processing time. The -rem option strips metadata chunks like text comments, timestamps, and color profiles to further reduce size.

PARAMETERS

INPUT

Input PNG file.

OUTPUT

Output PNG file.

-ow

Overwrite the input file in place.

-d DIRECTORY

Write output files to the specified directory.

-rem CHUNK

Remove a specified ancillary chunk. Use alla to remove all text chunks, or allb to remove all non-critical chunks.

-brute

Try all 148 filter/compression combinations for maximum reduction.

-reduce

Reduce color depth and bit depth where possible without data loss.

-l LEVEL

Set zlib compression level (0 = no compression, 9 = maximum).

-n

No output file; test compression without writing (useful for benchmarks).

-fix

Fix otherwise fatal conditions such as bad CRCs.

INSTALL

sudo apt install pngcrush

sudo dnf install pngcrush

sudo pacman -S pngcrush

sudo apk add pngcrush

sudo zypper install pngcrush

brew install pngcrush

nix profile install nixpkgs#pngcrush

CAVEATS

All optimization is lossless; image data is preserved exactly. The -brute option can be very slow on large images as it tests all 148 compression strategies. The -ow flag creates a temporary file and replaces the original, so sufficient disk space is needed. Does not support animated PNGs (APNG).

HISTORY

pngcrush was created by Glenn Randers-Pehrson and has been one of the oldest and most widely used PNG optimization tools, first released in 1998.