WordPress at a glance
function is not described

wp_default_editor() WP 2.5.0

Find out which editor should be displayed by default.

Works out which of the two editors to display as the current editor for a user. The 'html' setting is for the "Text" editor tab.

Hooks in function
Return

String. Either 'tinymce', or 'html', or 'test'

Usage

wp_default_editor();

Code of wp default editor: wp-includes/general-template.php WP 5.2.1

<?php
function wp_default_editor() {
	$r = user_can_richedit() ? 'tinymce' : 'html'; // defaults
	if ( wp_get_current_user() ) { // look for cookie
		$ed = get_user_setting( 'editor', 'tinymce' );
		$r  = ( in_array( $ed, array( 'tinymce', 'html', 'test' ) ) ) ? $ed : $r;
	}

	/**
	 * Filters which editor should be displayed by default.
	 *
	 * @since 2.5.0
	 *
	 * @param string $r Which editor should be displayed by default. Either 'tinymce', 'html', or 'test'.
	 */
	return apply_filters( 'wp_default_editor', $r );
}