As an alternative to this, I quite like https://squoosh.app/ - Also works on-device, but additionally it's open source, supports multiple output formats, and exposes all the speed / quality / transparency options.
Squoosh is great but for average user dealing with so many peremeters feels overwhelming and provides odd results.When you're handling a large number of files - like a Midjourney archive or a collection of images,it’s more convenient to use an app with preset settings that can process them in bulk, rather than one with detailed options that require fine-tuning.
I would suggest avoid using in Firefox, the images can appear to be brighter than converting in other browsers.
Sidenote, but I enjoyed seeing the squoosh maintainers talk through [1] how they diagnosed and resolved a memory leak they had a while back.