URL redirection

URL redirection, also called URL forwarding, is a World Wide Web technique for making a web page available under more than one URL address. When a web browser attempts to open a URL that has been redirected, a page with a different URL is opened. Similarly, domain redirection or domain forwarding is when all pages in a URL domain are redirected to a different domain, as when and are automatically redirected to . URL redirection is done for various reasons: for URL shortening; to prevent broken links when web pages are moved; to allow multiple domain names belonging to the same owner to refer to a single web site; to guide navigation into and out of a website; for privacy protection; and for less innocuous purposes such as phishing attacks.

There are several reasons to use URL redirection:

A user might mistype a URL, for example, "example.com" and "exmaple.com". Organizations often register these "misspelled" domains and redirect them to the "correct" location: example.com. The addresses example.com and example.net could both redirect to a single domain, or web page, such as example.org. This technique is often used to "reserve" other top-level domains (TLD) with the same name, or make it easier for a true ".edu" or ".net" to redirect to a more recognizable ".com" domain.

Web pages may be redirected to a new domain for three reasons:

With URL redirects, incoming links to an outdated URL can be sent to the correct location. These links might be from other sites that have not realized that there is a change or from bookmarks/favorites that users have saved in their browsers. The same applies to search engines. They often have the older/outdated domain names and links in their database and will send search users to these old URLs. By using a "moved permanently" redirect to the new URL, visitors will still end up at the correct page. Also, in the next search engine pass, the search engine should detect and use the newer URL.

The access logs of most web servers keep detailed information about where visitors came from 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 outgoing 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 technique bears the downside of the delay caused by the additional request to the original website's server. As this added request will leave a trace in the server log, revealing exactly which link was followed, it can also be a privacy issue. The same technique is also used by some corporate websites to implement a statement that the subsequent content is at another site, and therefore not necessarily affiliated with the corporation. In such scenarios, displaying the warning causes an additional delay.

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