Metadata (postmeta) (category)
| delete_post_meta_by_key() | Deletes all meta-fields (custom fields) of all posts by the specified meta-field key. |
| wp_generate_attachment_metadata() | Generates metadata for the image attachment and creates intermediate copies of the image - thumbnails of all registered sizes. |
| wp_get_attachment_metadata() | Retrieves the metadata for an attached file (attachment). |
| wp_maybe_generate_attachment_metadata() | Creates attachment metadata if it is missing; otherwise, does nothing. |
| wp_read_audio_metadata() | Gets all data about an audio file from its ID3 tags. This includes all available data: format, channels, bitrate, size, MIME type, duration, year, album, artist, comment, picture, etc. |
| wp_update_attachment_metadata() | Updates attachment (media file) metadata. |