A powerfull feature of ImageManager is the image usage. ImageManager will tell you if an image is being used and where. ImageManager will look through your website and database to find images and index the ones it found. In the navigator you can quickly see what images are being used; these images are indicated by a green bar. Images that are not used are indicated with a red bar.
If ImageManager finds an image that is being used, the directories in the navigator and sidebar will also receive a green bar. You can quickly see, at the top level of the directory tree, where used images are located.
False-positives and a word of caution
ImageManager will search for full paths, but some extensions have their own system to manage images. It can be possible that ImageManager cannot find the images thus declaring them unused. The usage status is a great indicator, but not always right. Please use the trash system and check your website thoroughly after moving images to the trash. We're trying to support as many extensions as possible.