Source

File: wp-includes/script-loader.php

function script_concat_settings() {
	global $concatenate_scripts, $compress_scripts, $compress_css;

	$compressed_output = ( ini_get( 'zlib.output_compression' ) || 'ob_gzhandler' === ini_get( 'output_handler' ) );

	if ( ! isset( $concatenate_scripts ) ) {
		$concatenate_scripts = defined( 'CONCATENATE_SCRIPTS' ) ? CONCATENATE_SCRIPTS : true;
		if ( ( ! is_admin() && ! did_action( 'login_init' ) ) || ( defined( 'SCRIPT_DEBUG' ) && SCRIPT_DEBUG ) ) {
			$concatenate_scripts = false;
		}
	}

	if ( ! isset( $compress_scripts ) ) {
		$compress_scripts = defined( 'COMPRESS_SCRIPTS' ) ? COMPRESS_SCRIPTS : true;
		if ( $compress_scripts && ( ! get_site_option( 'can_compress_scripts' ) || $compressed_output ) ) {
			$compress_scripts = false;
		}
	}

	if ( ! isset( $compress_css ) ) {
		$compress_css = defined( 'COMPRESS_CSS' ) ? COMPRESS_CSS : true;
		if ( $compress_css && ( ! get_site_option( 'can_compress_scripts' ) || $compressed_output ) ) {
			$compress_css = false;
		}
	}
}