WordPress at a glance
filter is not described

media_upload_default_type filter-hook . WP 2.5.0

Filters the default media upload type in the legacy (pre-3.5.0) media popup.

Usage

add_filter( 'media_upload_default_type', 'filter_function_name_1156' );
function filter_function_name_1156( $type ){
	// filter...

	return $type;
}
$type(string)
The default media upload type. Possible values include 'image', 'audio', 'video', 'file', etc.
Default: 'file'

Where the hook is called

In file: /wp-admin/media-upload.php
media_upload_default_type
wp-admin/media-upload.php 63
$type = apply_filters( 'media_upload_default_type', 'file' );

Where the hook is used (in WP core)

Does not used.