Optimizing PNGs with zopflipng -m in the oxygen-icons5 git tree would save 3M+ in total size (tested with zopflipng from zopfli 1.0.1) with no downsides I'm aware of. For example: find -name "*.png" -printf "%p %p\n" | xargs -L 1 -P 4 zopflipng -ym (A similar run with optipng -o7 would save ~1M) Reproducible: Always https://github.com/google/zopfli
thanks for the information as oxygen is more in maintenance mode than in active development I don't want to change all png files to save 10% disk space. I hope this is ok for you otherwise you can submit me the optimized files in a zip file and I'll check the differences.