I've had the same WordPress blog for years upon years, and years ago, I installed the Simple Image Sizes plugin to control image sizes. I think I wanted an easy way to set the size of post header images.
I didn't document things well, though, so I added a bunch of image sizes and now, years and at least one theme change later, I don't have any idea where those image sizes I added are actually used in my site, if at all.
According to my Media page and the Simple Image Sizes plugin, in addition to thumbnail, medium, and large image sizes, I also have the following:
I'd like to remove the unused image size definitions if possible, since they're causing massive storage bloat with each uploaded image, but I don't know which of them are unused.
More experienced WordPress admins: how would you go about locating where in plugin and theme files, if anywhere, those image sizes are used?