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HTTP referer

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This is an old revision of this page, as edited by Eliashc (talk | contribs) at 20:41, 18 January 2007. The present address (URL) is a permanent link to this revision, which may differ significantly from the current revision.

For the rare occasions where de-referring links is needed in Wikipedia, see Template:Derefer.

The referrer, or HTTP referrer, identifies, from the point of view of a internet webpage or resource, the address of the webpage (commonly the URL, the more generic URI or the i18n updated IRI) of the resource which links to it. By checking the referrer, the new page can see where the request came from. referrer logging is used to allow websites and web servers to identify where people are visiting them from, for promotional or security purposes. Since the referrer can easily be spoofed (faked), however, it is of limited use in this regard except on a casual basis.

A dereferrer is a means to strip the details of the referring website from a link request so that the target website cannot identify the page which was clicked on to originate a request.

More

When visiting a webpage, the referrer or referring page is the URL of the previous webpage from which a link was followed.

More generally, a referrer is the URL of a previous item which led to this request. The referrer for an image, for example, is generally the HTML page on which it is to be displayed. The referrer is part of the HTTP request sent by the browser program to the web server.

Many web sites log referrers as part of their attempt to track their users. Most web log analysis software can process this information. As referrer information can violate privacy, some browsers allow the user to disable the sending of referrer information. Some proxy and firewall software will also filter out referrer 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 referrer 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 referrer, which usually prevents these problems while still not divulging the user's last visited site.

Recently many blogs have started publishing referrer 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 referrer spam: the sending of fake referrer information in order to popularize the spammer's site.

Many pornographic paysites utilize referrer 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. Referrer spoofing is often used to gain free access to these sites.

Blocking referrer Information from within your Browser

If you use Firefox you can block sending referrer information by following these steps: 

  1. In the address bar of your Firefox browser type: about:config and hit Enter.
  2. In the Filter input field type: network.http.sendreferrerHeader.
  3. Double click on the preference name.
  4. Change the value from 2 to 0 and hit OK.


Dereferrer

Since a web server and site can log where visitors have apparently arrived from (ie the page which was clicked to reach the page they are loading), there are a number of dereferrer services, which allow web pages to link to others without giving referrer information. An example of a derefered link using a common dereferrer service is:

In the above example, your browser first goes to the ultimod.org site and then is redirected to en.wikipedia.org. To the wikipedia server it appears that there is no referrer, instead of this page, which would normally be considered the referring page.

See also

  • referrer spoofing, changing referrer information to gain unauthorized access to a web site.
  • referrer spam, providing fake referrer information in order to popularize a spammer's website.
  • RFC 2616: Hypertext Transfer Protocol – HTTP/1.1
  • HTTP_referrer test – displays the referrer (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 referrers to the page
  • E-referrer.com - User customized referrer list. When code is placed on your web page it will show the referrers in real time.
  • IRI – Internationalized Resource Identifiers
  • anonym.to - most popular Dereferrer service, ranked in the Alexa Top500
  • ReferHide.com - New-Age Dereferrer
  • Edie Awad's Blog - Blocking referrer information in Firefox Browser
  • Ultimod - another Dereferrer
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