Rarely used (category)

attachment_url_to_postid()

Tries to convert an attachment URL into a post ID.

get_allowed_mime_types()

Retrieve list of allowed mime types and file extensions.

wp_get_audio_extensions()

Returns a filtered list of WP-supported audio formats.

wp_get_ext_types()

Retrieves the list of common file extensions and their types.

wp_get_video_extensions()

Returns a filtered list of WP-supported video formats.

wp_read_image_metadata()

Get extended image metadata, exif or iptc as available.