URL shortening
URL shortening is a technique on the World Wide Web in which a Uniform Resource Locator may be made substantially shorter and still direct to the required page. This is achieved by using a redirect which links to the web page that has a long URL. For example, the URL "" can be shortened to "". Often the redirect domain name is shorter than the original one. A friendly URL may be desired for messaging technologies that limit the number of characters in a message, for reducing the amount of typing required if the reader is copying a URL from a print source, for making it easier for a person to remember, or for the intention of a permalink. In November 2009, the shortened links of the URL shortening service Bitly were accessed 2.1 billion times.
Other uses of URL shortening are to "beautify" a link, track clicks, or disguise the underlying address. This is because the URL shortener can redirect to just about any web domain, even malicious ones. So, although disguising of the underlying address may be desired for legitimate business or personal reasons, it is open to abuse. Some URL shortening service providers have found themselves on spam blocklists, because of the use of their redirect services by sites trying to bypass those very same blocklists. Some websites prevent short, redirected URLs from being posted.
Purposes
There are several reasons to use URL shortening. Often regular unshortened links may be aesthetically unpleasing. Many web developers pass descriptive attributes in the URL to represent data hierarchies, command structures, transaction paths or session information. This can result in URLs that are hundreds of characters long and that contain complex character patterns. Such URLs are difficult to memorize, type out or distribute. As a result, long URLs must be copied and pasted for reliability. Thus, short URLs may be more convenient for websites or hard copy publications, the latter often requiring that very long strings be broken into multiple lines or truncated.On Twitter and some instant messaging services, there is a limit to the number of characters a message can carry however, Twitter now shortens links automatically using its own URL shortening service,, so there is no need to use a separate URL shortening service just to shorten URLs in a tweet. On other such services, using a URL shortener can allow linking to web pages which would otherwise violate this constraint. Some shortening services, such as and can generate URLs that are human-readable, although the resulting strings are longer than those generated by a length-optimized service. Finally, URL shortening sites provide detailed information on the clicks a link receives, which can be simpler than setting up an equally powerful server-side analytics engine, and unlike the latter, does not require any access to the server.
URLs encoded in two dimensional barcodes such as QR code are often shortened by a URL shortener in order to reduce the printed area of the code, or allow printing at lower density in order to improve scanning reliability.
Registering a short URL
Some websites create short links to make sharing links via instant messaging easier, and to make it cheaper to send them via SMS. This can be done online, at the web pages of a URL shortening service; to do it in batch via bulk upload with tools like CSV importer or on demand may require the use of an API.A few well-known websites have set up their own URL shortening services for their own use for example, Twitter with t.co, Telegram with t.me, Google with g.co, and GoDaddy with x.co.
Techniques
In URL shortening, every long URL is associated with a unique key, which is the part after its top-level domain name. For example, has a key of, these keys are case-sensitive most of the time and using the wrong case may lead to a different destination URL. Not all redirection is treated equally; the redirection instruction sent to a browser can contain in its header HTTP response status codes such as 301, 302, 307 or 308.There are several techniques to implement URL shortening. Keys can be generated in base 36, assuming 26 letters and 10 numbers. In this case, each character in the sequence will be. Alternatively, if uppercase and lowercase letters are differentiated, then each character can represent a single digit within a number of base 62. In order to form the key, a hash function can be made, or a random number generated so that key sequence is not predictable. Or users may propose their own custom keys. For example, can be shortened to.
Not all URI schemes are capable of being shortened as of 2011, although URI schemes such as,,,,,,,,,,,,,,, and are being addressed by such services as URL shorteners. Typically, Data URI scheme| and URLs are not supported for security reasons. Some URL shortening services support the forwarding of URLs, as an alternative to address munging, to avoid unwanted harvest by web crawlers or bots. This may sometimes be done using short, CAPTCHA-protected URLs, but this is not common.
Makers of URL shorteners usually register domain names with less popular or esoteric Top-level domains in order to achieve a short URL and a catchy name, often using domain hacks.
This results in registration of different URL shorteners with a myriad of different countries, leaving no relation between the country where the domain has been registered and the URL shortener itself or the shortened links. Top-level domains of countries such as Libya, Samoa, Mongolia, Malaysia and Liechtenstein have been used as well as many others. In some cases, the political or cultural aspects of the country in charge of the top-level domain may become an issue for users and owners, but this is not usually the case.
Services may record inbound statistics, which may be viewed publicly by others.
Expiry and time-limited services
While many providers claim their shortened URLs won't expire for as long as the service is provided, they may decide to discontinue the service at any time.A permanent URL is not necessarily a good thing. There are security implications, and obsolete short URLs remain in existence and may be circulated long after they cease to point to a relevant or even extant destination. Sometimes a short URL is useful simply to give someone over a telephone conversation for a one-off access or file download, and no longer needed within a couple of minutes.
Some providers offer expiration on shortened URLs. This may include URLs that expire after a certain amount of time, on a certain date or after a certain number of usages.
A Microsoft Security Brief recommends the creation of short-lived URLs, but for reasons explicitly of security rather than convenience.
History
An early reference is US Patent , which describes...a system, method and computer program product for providing links to remotely located information in a network of remotely connected computers. A uniform resource locator is registered with a server. A shorthand link is associated with the registered URL. The associated shorthand link and URL are logged in a registry database. When a request is received for a shorthand link, the registry database is searched for an associated URL. If the shorthand link is found to be associated with a URL, the URL is fetched, otherwise an error message is returned.
The patent was filed in September 2000; while the patent was issued in 2005, US patent applications are made public within 18 months of filing.
Another reference to URL shortening was in 2001. The first notable URL shortening service, TinyURL, was launched in 2002. Its popularity influenced the creation of at least 100 similar websites, although most are simply domain alternatives. Initially, Twitter automatically translated URLs longer than twenty-six characters using TinyURL, although it began using bit.ly instead in 2009 and later developed its own URL shortening service, t.co.
On 14 August 2009 WordPress announced the wp.me URL shortener for use when referring to any WordPress.com blog post. In November 2009, shortened links on bit.ly were accessed 2.1 billion times. Around that time, bit.ly and TinyURL were the most widely used URL-shortening services.
One service, tr.im, stopped generating short URLs in 2009, blaming a lack of revenue-generating mechanisms to cover costs and Twitter's default use of the bit.ly shortener, and questioning whether other shortening services could be profitable from URL shortening in the longer term. It resumed for a time, then closed.
The shortest possible long-term URLs were generated by NanoURL from December 2009 until about 2011, associated with the top-level .to domain, in the form, where represents a sequence of random numbers and letters.
On 14 December 2009 Google announced a service called Google URL Shortener at goo.gl, which originally was only available for use through Google products and extensions for Google Chrome. On 21 December 2009, Google introduced a YouTube URL Shortener, youtu.be. From September 2010 Google URL Shortener became available via a direct interface. The goo.gl service provides analytics details and a QR code generator. On 30 March 2018 Google announced that it is "turning down support for goo.gl over the coming weeks and replacing it with Firebase Dynamic Links". On July 18, 2024, Google announced that existing Google URL shortener URLs will stop working as of August 25, 2025. However, as of August 1, 2025, Google announced that they will only deactivate links that have shown no traffic since late 2024.