I've tried a few, the best one was pingo (https://css-ig.net/pingo). Pingo -s9 gives better results than oxipng with Zopfli, while being usually two order of magnitudes faster. It's also faster than "regular" oxipng while being better. I can usually shave of 15%/20% of the size of png files I encounter. One thing I didn't check is that you might pay that in decoding time, I've never seen anybody talking about that... - Source: Hacker News / almost 2 years ago

Pinga, GUI for Pingo (https://css-ig.net/pingo) for lossless photo compression while keeping the metadata. Source: almost 3 years ago

I tried it on the Firefox and Tor Browser on Whonix, same error pops up because it's using the Tor network? Is there any way I can bypass this error so I can visit my schools website, or another way to use the site anonymously? Site is Clever. Source: over 1 year ago

Mine also don't know what bookmarks are. So to get into Schoology, they type clever.com into the search bar - not the address bar - then log into it, then click the student page, then find Schoology, then click it. And the wifi in my part of the building sucks, so it takes them 5 minutes. Source: over 1 year ago