LoyaltyHarbour Image Optimizer

This app is a must-have. For less than $5, I saved myself a whole day's worth of individually compressing and re-uploading images to my site.

Shopify stores tend to be slow. Compressing your images will definitely help!

Note: Since Shopify uses a CDN, the changes won't be drastic, and won't be evident for a day or two. If you compress your images and then immediately run a new speed test, you will most likely be re-testing a cached (i.e. uncompressed) version of your photo, and therefore won't see much, if any change.