In a previous article, I mentioned how WordPress doesn’t provide information to locate posts where an attachment is in use. Comments to the article indicate others are interested in having this information as well. Find Posts Using Attachment created by Sergey Biryukov, is an easy to use plugin that solves this problem.
The plugin adds a Used In column to the list view in the media library as well as to the attachment details modal. Not only can you find posts that use the image in a post or as a featured image, it works with custom post types too.
Although it’s primarily for images, it also tells you where other attachment types are used in posts such as mp3s or text files. If you need to change or update attachments in the media library but don’t remember where they’re being used, this plugin is invaluable.