Duplicate response headers should be shown individually if that is how they were sent Test: <?php header("X-Test-Header: Alpha", false); header("X-Test-Header: Beta", false); ?> Steps to Reproduce: 1. Inspect test page 2. Observe Response Headers for main resource Expected: X-Test-Header: Alpha X-Test-Header: Beta Actual: X-Test-Header: Alpha, Beta Notes: * While technically equivalent, I'd rather see what actually instead of some reformulation: $ curl --verbose .../test.php ... < HTTP/1.1 200 OK < Date: Wed, 05 Apr 2017 18:22:24 GMT < Server: Apache/2.4.25 (Unix) PHP/5.6.30 < X-Powered-By: PHP/5.6.30 < X-Test-Header: Alpha < X-Test-Header: Beta < Content-Length: 19 < Content-Type: text/html; charset=UTF-8 ...