URL redirection



There are several reasons for a webmaster or developer to use redirection:

Similar domain names

A web browser user might mis-type a URL -- for example, "" and "". Organizations often register these "mis-spelled" domains and re-direct them to the "correct" location: For example: the addresses and could both redirect to a single domain, or web page, such as This technique is often used to "reserve" other TLDs with the same name, or make it easier for a true ".edu" or ".net" to redirect to a more recognizable ".com" domain.

Moving a site to a new domain

Why redirect a web page?

  • A web site might need to change its domain name.
  • An author might move his or her pages to a new domain.
  • Two web sites might merge.



Logging outgoing links

The access logs of most web servers keep detailed information from where visitors came and how they browsed the hosted site. They do not, however, log which links visitors left by. This is because the visitor's browser has no need to communicate with the original server when the visitor clicks on an out-going link.

This information can be captured in several ways. One way involves URL redirection. Instead of sending the visitor straight to the other site, links on the site can direct to a URL on the original website's domain that automatically redirects to the real target. This added request will leave a trace in the server logs saying exactly which link was followed. This technique is also used by some corporate websites to have a "warning" page that the content is off-site and not necessarily affiliated with the corporation. This technique does bear the downside in the delay of an additional request to the original website's server. For websites that wish to display a "warning" page before automatically forwarding, the length of time the warning is displayed is an additional delay.

Short, meaningful, persistent aliases for long or changing URLs

Currently, web engineers tend to pass descriptive attributes in the URL to represent data hierarchies, command structures, transaction paths and session information. This results in a URL that is aesthetically unpleasant and difficult to remember. Sometimes the URL of a page changes even though the content stays the same.

Manipulating search engines

Some years ago, redirect techniques were used to fool search engines. For example, one page could show popular search terms to search engines but redirect the visitors to a different target page. There are also cases where redirects have been used to "steal" the page rank of one popular page and use it for a different page, usually involving the 302 HTTP status code of "moved temporarily."

Search engine providers noticed the problem and took appropriate actions. Usually, sites that employ such techniques to manipulate search engines are punished automatically by reducing their ranking or by excluding them from the search index.


Satire and criticism

In the same way that a Google bomb can be used for satire and political criticism, a domain name that conveys one meaning can be redirected to any other web page, sometimes with malicious intent.

Manipulating visitors



There are several techniques to implement a redirect. In many cases, Refresh meta tag is the simplest one. However, there exist several strong opinions discouraging this method.

Manual redirect

The simplest technique is to ask the visitor to follow a link to the new page, usually using an HTML anchor as such: Please follow link! This method is often used as a fall-back for automatic methods — if the visitor's browser does not support the automatic redirect method, the visitor can still reach the target document by following the link.

HTTP status codes 3xx

In the [] computer protocol used by the World Wide Web, a redirect is a response with a status code beginning with 3 that induces a browser to go to another location.

The HTTP standard defines several status codes for redirection:

  • 300 multiple choices (e.g. offer different languages)
  • 301 moved permanently
  • 302 found (e.g. temporary redirect)
  • 307 temporary redirect

All of these status codes require that the URL of the redirect target is given in the Location: header of the HTTP response. The 300 multiple choices will usually list all choices in the body of the message and show the default choice in the Location: header.

Within the 3xx range, there are also some status codes that are quite different from the above redirects (they are not discussed here with their details):

  • 304 not modified
  • 305 use proxy

This is a sample of a HTTP response that uses the 301 "moved permanently" redirect:

HTTP/1.1 301 Moved Permanently Location: Content-Type: text/html Content-Length: 174



This page has moved to

Using server-side scripting for Redirection

Often, web authors don't have sufficient permissions to produce these status codes: The HTTP header is generated by the web server program and not read from the file for that URL. Even for CGI scripts, the web server usually generates the status code automatically and allows custom headers to be added by the script. To produce HTTP status codes with cgi-scripts, one needs to enable non-parsed-headers.

Sometimes, it is sufficient to print the "Location: 'url'" header line from a normal CGI script. Many web servers choose one of the 3xx status codes for such replies.

Frameworks for server-side content generation typically require that HTTP headers be generated before response data. As a result, the web programmer who is using such a scripting language to redirect the user's browser to another page must ensure that the redirect is the first or only part of the response. In the ASP scripting language, this can also be accomplished using the methods response.buffer=true and response.redirect "". Using PHP, one can use header("Location:");.

According to the HTTP protocol, the Location header must contain an absolute URI. When redirecting from one page to another within the same site, it is a common mistake to use a relative URI. As a result most browsers tolerate relative URIs in the Location header, but some browsers display a warning to the end user.

Using .htaccess for Redirection

When using the Apache web server, directory-specific .htaccess files (as well as apache's main configuration files) can be used. For example, to redirect a single page: Redirect 301 /oldpage.html

To change domain names: RewriteEngine On

RewriteCond %{HTTP_HOST} ^.*$ [NC] RewriteRule ^(.*)$$1 [R=301,L]

Use of .htaccess for this purpose usually does not require administrative permissions, though it can be disabled. When you have access to apache main config file (such as httpd.conf), it is best to avoid the use of .htaccess files.

Refresh Meta tag and HTTP refresh header

Netscape introduced a feature to refresh the displayed page after a certain amount of time. This method is often called meta refresh. It is possible to specify the URL of the new page, thus replacing one page after some time by another page:

A timeout of 0 seconds means an immediate redirect.



Please follow link!

  • This technique is usable by all web authors because the meta tag is contained inside the document itself.
  • Note the strange syntax of the content field.
  • The number "0" in this example may be replaced by another number to achieve a delay of as many seconds.
  • Many users regard a delay of this kind as annoying unless there is a reason for it.
  • This is a proprietary/non-standard extension by Netscape. It is supported by most web browsers.

This is an example of achieving the same effect by issuing a HTTP refresh header:

HTTP/1.1 200 ok Refresh: 0; url= Content-type: text/html Content-length: 78

Please follow link! This response is easier to generate by CGI programs because one does not need to change the default status code. Here is a simple CGI program that effects this redirect:

  1. !/usr/bin/perl

print "Refresh: 0; url="; print "Content-type: text/htmlrn"; print "rn"; print "Please follow link!" Note: Usually, the HTTP server adds the status line and the Content-length header automatically.

This method is considered by the W3C to be a poor method of redirection, since it does not communicate any information about either the original or new resource, to the browser (or search engine). The W3C's Web Content Accessibility Guidelines (7.4) discourage the creation of auto-refreshing pages, since most web browsers do not allow the user to disable or control the refresh rate. Some articles that they have written on the issue include W3C Web Content Accessibility Guidelines (1.0): Ensure user control of time-sensitive content changes and Use standard redirects: don't break the back button!

JavaScript redirects

JavaScript offers several ways to display a different page in the current browser window. Quite frequently, they are used for a redirect. However, there are several reasons to prefer HTTP header or the refresh meta tag (whenever it is possible) over JavaScript redirects:

  • There are several reasons for some users to disable JavaScript:
    • Security considerations
    • Some browsers don't support JavaScript
    • many crawlers (e.g. from search engines) don't execute JavaScript.
  • There is no "standard" way of doing it: A search for "you are being redirected" will find that virtually each JavaScript redirect employs different methods. This makes it difficult for Web client programmers to honor your redirect request without implementing all of JavaScript.

Frame redirects


<pre wrap> <body>Please follow <a id="ref_result" href="">link</a>!</body></pre>


This technique is commonly called cloaking. This may be used so that the reader sees a more memorable URL or, with fraudulent intentions, to conceal a phishing site as part of website spoofing.

Redirect loops

It is quite possible that one redirect leads to another redirect. For example, the URL (note the differences in the domain name) is first redirected to and again redirected to the correct URL: This is appropriate: the first redirection corrects the wrong domain name. The second redirection selects the correct language section. Finally, the browser displays the correct page.

Sometimes, however, a mistake can cause the redirection to point back to the first page, leading to an infinite loop of redirects. Browsers usually break that loop after a few steps and display an error message instead.

The HTTP standard states:




There exist services that can perform URL redirection on demand, with no need for technical work or access to the webserver your site is hosted on.

URL redirection services



URL obfuscation services

There exist redirection services for hiding the referrer using META refresh, such as and

This is very easy to do with PHP, such as in this example. $u=htmlspecialchars($_GET['url']); // used to sanitise the code ?> Redirect

You should be able to be redirected to . This code can then be accessed by example,
If the input is not sanitized (using htmlspecialchars()) someone could be supplied with a URL that executes some malicious JavaScript appearing to originate from the website hosting the PHP code.

Further, the above example code may not work correctly with URLs containing variables, unless the input is first encoded, or code is added that loops across the $_GETs and pieces together the final URL.

See also


External links

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