jStrip is described as 'Free tool to reduce the file size of JPEG images without sacrificing image quality. High-traffic websites with many JPEG images can benefit from decreased bandwidth costs. Less hard disk space will be used by image collectors' and is a Image Optimizer in the photos & graphics category. There are more than 25 alternatives to jStrip for a variety of platforms, including Windows, Mac, Linux, Web-based and BSD apps. The best jStrip alternative is ImageOptim. It's not free, so if you're looking for a free alternative, you could try ImageOptim or RIOT - Radical Image Optimization Tool. Other great apps like jStrip are PNGGauntlet, Oxipng, pngquant and Pingo - image optimizer for web.
JStrip just removes metadata it does not attempt to compress or optimise the image in any way.