Source

File: wp-includes/class-wp-editor.php

private static function default_settings() {
		global $tinymce_version;

		$shortcut_labels = array();

		foreach ( self::get_translation() as $name => $value ) {
			if ( is_array( $value ) ) {
				$shortcut_labels[ $name ] = $value[1];
			}
		}

		$settings = array(
			'theme'                        => 'modern',
			'skin'                         => 'lightgray',
			'language'                     => self::get_mce_locale(),
			'formats'                      => '{' .
				'alignleft: [' .
					'{selector: "p,h1,h2,h3,h4,h5,h6,td,th,div,ul,ol,li", styles: {textAlign:"left"}},' .
					'{selector: "img,table,dl.wp-caption", classes: "alignleft"}' .
				'],' .
				'aligncenter: [' .
					'{selector: "p,h1,h2,h3,h4,h5,h6,td,th,div,ul,ol,li", styles: {textAlign:"center"}},' .
					'{selector: "img,table,dl.wp-caption", classes: "aligncenter"}' .
				'],' .
				'alignright: [' .
					'{selector: "p,h1,h2,h3,h4,h5,h6,td,th,div,ul,ol,li", styles: {textAlign:"right"}},' .
					'{selector: "img,table,dl.wp-caption", classes: "alignright"}' .
				'],' .
				'strikethrough: {inline: "del"}' .
			'}',
			'relative_urls'                => false,
			'remove_script_host'           => false,
			'convert_urls'                 => false,
			'browser_spellcheck'           => true,
			'fix_list_elements'            => true,
			'entities'                     => '38,amp,60,lt,62,gt',
			'entity_encoding'              => 'raw',
			'keep_styles'                  => false,
			'cache_suffix'                 => 'wp-mce-' . $tinymce_version,
			'resize'                       => 'vertical',
			'menubar'                      => false,
			'branding'                     => false,

			// Limit the preview styles in the menu/toolbar.
			'preview_styles'               => 'font-family font-size font-weight font-style text-decoration text-transform',

			'end_container_on_empty_block' => true,
			'wpeditimage_html5_captions'   => true,
			'wp_lang_attr'                 => get_bloginfo( 'language' ),
			'wp_keep_scroll_position'      => false,
			'wp_shortcut_labels'           => wp_json_encode( $shortcut_labels ),
		);

		$suffix  = SCRIPT_DEBUG ? '' : '.min';
		$version = 'ver=' . get_bloginfo( 'version' );

		// Default stylesheets.
		$settings['content_css'] = includes_url( "css/dashicons$suffix.css?$version" ) . ',' .
			includes_url( "js/tinymce/skins/wordpress/wp-content.css?$version" );

		return $settings;
	}