What is a P3P HTTP header?
P3P is a protocol that you place in the response headers of the website. The P3P header allows websites to explain their intended use of information that the visitor leaves behind on the website. P3P is an abbreviation for "Platform for Privacy Preferences Project".
The P3P HTTP header tag contains a list of privacy features, which are listed in the "compact policy" (CP) feature. In the compact policy, you'll find a list of abbreviations that explains which private information of the visitor is actually being collected.
Another feature in the P3P HTTP header is the "policyref" feature. The policyref is a link to an XML file. This XML file contains the extensive information of the privacy statement.