Smush.it uses optimization methods, specific to different image formats, and removes junk bytes from image files. This tool works without quality loss or change in the appearance of images.. After image processing Smush.it reports how many bytes will be saved and how much percentage the image has been optimized. Linking to images from the service is not worth it., as they are not always available.

For lovers WordPress I suggest installing a special plugin that works on the basis of the service Smush.it. The plugin is called WP Smush.it. Can optimize as per picture, so all at once.

You can download the plugin here.

Developer site WP Smush.it.

Download from repository here.