Which HTTP request headers are used by Piwik PRO?

When measuring activity with the Piwik PRO tracking API, the following HTTP headers may be used:

• Host – the hostname of the HTTP request, the hostname of the Piwik PRO server;
• Referrer – used to track Referrer information such as website, search engine, social network;
• User-Agent – used to detect the information about browsers, operating system, devices by the device-detector library;
• Cookie – when Opted-out from tracking, or when Third party cookies are used;
• Origin – used when cross-origin resource sharing is enabled;
• Accept-Language – used to detect the users’ language;
• X-Forwarded-Proto, X-Forwarded-Host, X-Forwarded-For – when Piwik PRO is set up behind a proxy;
• DNT – used to detect whether a visitor’s device is opted-out from tracking.