How does webpagetest check if an image can be compressed??!?

How come when I save images at 70 quality level in PS then run it though JPEGmini and JPEGtran and still WPT is telling me they need to be compressed? What can you possible do more to compress them???

Do you have a link to a result? If you go to the main waterfall view there is a link right below the waterfall for “view all images” and for the image there will be a link to see the optimization details.

If I had to guess it would be meta-data (exif data, color profiles, etc) in the file not the image itself.

Is WPT complaining about images on your server, or from an AD network? Perhaps a third party library?

I have noticed that SumoMe has an image that isn’t optimized (even though I asked them to optimize it…)

But I agree with pmeenan, meta data is very likely the cause.