Optimizing your images will helps your WordPress site load faster.
Download and activate WP Smush.it This plugin will optimize every image you upload and you can use the Bulk Smush.it feature to smush all of your uploaded images.
Alternatives to WP Smush.it include EWWW Image Optimizer, CW Image Optimizer, Imsanity and Hammy and Compress JPEG & PNG images
Many WordPress users prefer using these plugins as they do not rely on an external server to process your images.