I downloaded https://www.imgfiber.com/compare/original.jpg and dragged it into the try-it-now section - says it's now 1.3mb.
That's worse than Squoosh's default 897kb (https://squoosh.app/editor), though better than CompressorJS's default 2.21mb (https://fengyuanchen.github.io/compressorjs/), (edit ii) tho changing CompressorJS's quality setting to 0.75 results in the exact same output as ImgFiber.
Edit: this is on latest Chrome + macos.