IMHO these JPEG optimizers need to explain what optimization they actually do.
At the very least, it should mention if the optimization is lossless (by dropping metadata, optimizing Huffman table/progressive scan parameters etc.) or lossy: because they have very different use cases (sometimes you need the image to be pixel-wise identical).
Even better, if lossy, "how lossy" it is.
I'm aware it's using mozjpeg [1] which is pretty good (guetzli [2] is another good one for the interested); still, it comes with many settings and routines (both lossless and lossy) that can be configured.
At the very least, it should mention if the optimization is lossless (by dropping metadata, optimizing Huffman table/progressive scan parameters etc.) or lossy: because they have very different use cases (sometimes you need the image to be pixel-wise identical).
Even better, if lossy, "how lossy" it is.
I'm aware it's using mozjpeg [1] which is pretty good (guetzli [2] is another good one for the interested); still, it comes with many settings and routines (both lossless and lossy) that can be configured.
[1] https://github.com/mozilla/mozjpeg
[2] https://github.com/google/guetzli