Referer
From Free net encyclopedia
Referer is a common misspelling of the word "referrer"; so common, in fact, that it made it into the official specification of HTTP--the communication protocol of the World Wide Web. When visiting a webpage, the referer or referring page is the URL of the previous webpage from which a link was followed. More generally, it is the URL of a previous item which led to this request--the referer for an image, for example, is generally the HTML page on which it is to be displayed. The referer is part of the HTTP request sent by the browser program to the web server. The referer is also provided in the document.referer Javascript variable.
Many web sites log referers as part of their attempt to track their users. Most web log analysis software can process this information. As referer information can violate privacy, some browsers allow the user to disable the sending of referer information. Some proxy and firewall software will also filter out referer information, to avoid leaking the location of non-public websites. This can in turn cause problems: some servers block parts of their site to browsers that don't send the right referer information, in an attempt to prevent deep linking or unauthorised use of images (bandwidth theft). Some proxy software has the ability to give the top-level address of the target site as the referer, which usually prevents these problems while still not divulging the user's last visited site.
Recently many blogs have started publishing referer information in order to link back to people who are linking to them, and hence broaden the conversation. This has led, in turn, to the rise of referer spam: the sending of fake referer information in order to popularize the spammer's site.
Many pornographic paysites utilize referer information to secure their materials: only browsers arriving from a small set of approved (login-) pages are given access; this facilitates the sharing of materials among a group of cooperating paysites. Referer spoofing is used to gain free access to these sites.
References and external links
- RFC 2616: Hypertext Transfer Protocol -- HTTP/1.1
- HTTP_REFERER test - displays the referer (as well as all other HTTP headers) sent by your browser
- Referer.org - provides javascript code which, when added to a web page , displays the most common referers to the pagede:Referer