This plugin let you juxtapose 2 images with a slider that can be moved to show one image or the other.
With Juxtapose Images you can create beautiful effects like showing a picture in the past and compare with nowadays, or
a night/day contrast, a before and after view, etc…
Very easy to use, just use the [juxtapose]..[/juxtapose] shortcode, adding 2 images in between the shortcode. No configuration needed. Very little overhead in the loading speed. Only a small javascript and css is added when needed.