[web007]

ImageOptim is fantastic. You can use it via CLI, so I've added it to a few different archiving / publishing workflows in the past. One thing that some people don't realize is you can run it multiple times on the same (PNG) images and get better results. Each filter is dependent on the input from the previous filter, so running them again can give you better results even after one run. This works out because filter 3 might give you some savings or rearrange the data in a way that filter 1 can now take advantage of.

The other JPG filters are lossless, but be aware that Guetzli is lossy!

I was impressed with just how much it could losslessly compress some massive JPGs until I did a visual diff. I can't see the difference, like one-bit deltas sort of thing, but it's not 1:1 lossless as I would expect.