WordPress at a glance
action is not described

media_upload_(tab) action-hook . WP 2.5.0

Fires inside limited and specific upload-tab views in the legacy (pre-3.5.0) media popup.

The dynamic portion of the hook name, $tab, refers to the specific media upload tab. Possible values include 'library' (Media Library), or any custom tab registered via the 'media_upload_tabs' filter.

Usage

add_action( 'media_upload_(tab)', 'action_function_name_211' );
function action_function_name_211(){
	// action...
}

Where the hook is called

In file: /wp-admin/media-upload.php
media_upload_(tab)
wp-admin/media-upload.php 110
do_action( "media_upload_{$tab}" );

Where the hook is used (in WP core)

wp-admin/includes/admin-filters.php 19
add_action( 'media_upload_image', 'wp_media_upload_handler' );
wp-admin/includes/admin-filters.php 20
add_action( 'media_upload_audio', 'wp_media_upload_handler' );
wp-admin/includes/admin-filters.php 21
add_action( 'media_upload_video', 'wp_media_upload_handler' );
wp-admin/includes/admin-filters.php 22
add_action( 'media_upload_file', 'wp_media_upload_handler' );
wp-admin/includes/admin-filters.php 35
add_filter( 'media_upload_gallery', 'media_upload_gallery' );
wp-admin/includes/admin-filters.php 36
add_filter( 'media_upload_library', 'media_upload_library' );
wp-admin/includes/admin-filters.php 38
add_filter( 'media_upload_tabs', 'update_gallery_tab' );