!!! Overview
[{$pagename}] is a [HTTP Request Header] contains the address of the previous [web] page from which a link to the currently requested page was followed. 

[{$pagename}] allows servers to identify where people are visiting them from and may use that data for [analytics], [logging], or optimized [caching|Cache], for [example].

Note that referer is actually a misspelling of the word "referrer"


%%warning
[{$pagename}] has the potential to reveal information about the browsing history of the user, which is a [Privacy Considerations]. ([Unvalidated redirects and forwards])
%%
[{$pagename}] header [SHOULD NOT] not sent by [browsers] if:
* the referring resource is a local "file" or "data" [URI],
* an unsecured [HTTP] request is used and the referring page was received with a secure protocol ([HTTPS]).


!! More Information
There might be more information for this subject on one of the following:
[{ReferringPagesPlugin before='*' after='\n' }]
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* [#1] - [Referer|https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Referer|target='_blank'] - based on information obtained 2018-03-21-