We'll create fresh WordPress site with ResizeFly installed. You have 20 minutes to test the plugin after that site we'll be deleted.
Instead of creating image sizes on upload, this plugin only creates them when requested.
Normally after activating a new theme or plugin that adds new image sizes, you will have to use a tool like Regenerate Thumbnails to create the newly registered image sizes. Depending on the size of the media library and the “power” of your server, this might take a while or even take several tries to process all your images; and in the end, you don’t even know if you’ll need all of the resized images.
This plugin takes care of the resizing dynamically and creates the requested size the moment it is first requested—and only when it is requested.
For users: Please use the support forums on wordpress.org
For developers: Head over to the Github repository
For everything else, find me on twitter or on slack