WordPress Core
A featured image (also called a post thumbnail) is the primary image associated with a post, page or custom post type. It is stored separately from any images embedded in the post content and is typically used by themes to display a representative image in listing pages, headers and social sharing previews.
How featured images work
When you set a featured image, WordPress stores the attachment ID in wp_postmeta under the key _thumbnail_id. The theme retrieves this ID and displays the image using the_post_thumbnail() or get_the_post_thumbnail(). The actual file can be any image in the Media Library.
Featured images are separate from the post content. An image embedded in a Gutenberg block or Classic Editor content is not the featured image unless explicitly set as one. Removing an image from the post content does not unset the featured image, and vice versa.
Featured images and media governance
Because featured images are stored as metadata references (attachment IDs), they are covered by Mediapapa’s usage index. If you attempt to delete a file that is set as a featured image somewhere on the site, Deletion Warnings will flag it. Safe Replace will update the _thumbnail_id reference when replacing a file sitewide.
A common source of unused media on WordPress sites is old featured images from deleted or revised posts — the image remains in the library after the post is gone or after the featured image was changed to a different file.
Frequently asked questions
Is the featured image the same as an image embedded in post content?
No. Featured images are stored as postmeta references. Embedded images in content (Gutenberg blocks, Classic Editor) are inline references in the post body or block attributes. A post can have a featured image and also contain inline images — they are separate.
Can I have multiple featured images on one post?
Not natively. WordPress supports one featured image per post. Custom post types can define multiple “thumbnail” meta fields, but those require custom development. Standard themes and plugins expect a single featured image.
What happens to a featured image when I delete the source file?
The _thumbnail_id reference remains in the database, but the image no longer exists. The theme typically displays a broken image or nothing. Mediapapa’s Deletion Warnings prevent this by blocking deletion of any file set as a featured image on a live post.
Related terms: Attachment · Attachment ID · Usage Index · Deletion Warnings
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