Wikipedia

URL shortening

This is thelatest accepted revision,reviewedon15 November 2024.

For information about short URLs for pages on Wikipedia, seeWikipedia:URLShortener.

URL shorteningis a technique on theWorld Wide Webin which aUniform Resource Locator(URL) may be made substantially shorter and still direct to the required page. This is achieved by using aredirectwhich links to theweb pagethat has a long URL. For example, the URL "https://en.wikipedia.org/wiki/URL_shortening"can be shortened to"https://w.wiki/U".Often the redirectdomain nameis shorter than the original one. Afriendly URLmay be desired for messaging technologies that limit the number ofcharactersin a message (for example SMS), 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 apermalink.In November 2009, the shortened links of the URL shortening serviceBitlywere accessed 2.1 billion times.[1]

TheURL shorteneronMeta-Wiki

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.[2]Some URL shortening service providers have found themselves on spamblocklists,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

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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 (e.g. a printed magazine or a book), the latter often requiring that very long strings be broken into multiple lines (as is the case with somee-mailsoftware orinternet forums) or truncated.

OnTwitterand someinstant messagingservices, 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,t.co,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 asgoo.gl,tinyurl,andbit.lycan 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 asQR codeare 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

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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 anAPI.

A few well-known websites have set up their own URL shortening services for their own use – for example, Twitter with t.co,[3]Telegram with t.me, Google with g.co,[4]and GoDaddy with x.co.[5]

Techniques

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See also:URL redirection

In URL shortening, every long URL is associated with aunique key,which is the part after itstop-level domain name.For example,https://tinyurl /m3q2xthas a key ofm3q2xt,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 headerHTTP response status codessuch as 301 (moved permanently), 302 (found), 307 (temporary redirect) or 308 (permanent redirect).

There are several techniques to implement URL shortening. Keys can be generated inbase 36,assuming 26 letters and 10 numbers. In this case, each character in the sequence will be0, 1, 2,..., 9, a, b, c,..., y, z.Alternatively, if uppercase and lowercase letters are differentiated, then each character can represent a single digit within a number ofbase 62(26 + 26 + 10). In order to form the key, ahash functioncan be made, or arandom number generatedso that key sequence is not predictable. Or users may propose their own custom keys. For example,https://example /product?ref=01652&type=shirtcan be shortened tohttps://tinyurl /exampleshirt.

Not all URI schemes are capable of being shortened as of 2011, although URI schemes such ashttp,https,ftp,ftps,mailto,mms,rtmp,rtmpt,ed2k,pop,imap,nntp,news,ldap,gopher,dictanddnsare being addressed by such services as URL shorteners. Typically,data:andjavascript:URLs are not supported for security reasons (to combat attacks likecross-site scriptingandsession hijacking). Some URL shortening services support the forwarding ofmailtoURLs, as an alternative toaddress munging,to avoid unwanted harvest byweb crawlersorbots.This may sometimes be done using short,CAPTCHA-protected URLs, but this is not common.[6]

Makers of URL shorteners usually register domain names with less popular or esotericTop-level domainsin order to achieve a short URL and a catchy name, often usingdomain 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 domainsof countries such asLibya(.ly),Samoa(.ws),Mongolia(.mn),Malaysia(.my) andLiechtenstein(.li) have been used as well as many others. In some cases, the political or cultural aspects of the country in charge of thetop-level domainmay become an issue for users and owners,[7]but this is not usually the case.

Services may record inbound statistics, which may be viewed publicly by others.[8]

Expiry and time-limited services

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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.[citation needed]

A Microsoft Security Brief recommends the creation of short-lived URLs, but for reasons explicitly of security rather than convenience.[9]

History

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An early reference is US Patent6957224,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 (URL) 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.[10]

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.[11]The first notable URL shortening service,TinyURL,was launched in 2002. Its popularity influenced the creation of at least 100 similar websites,[12]although most are simply domain alternatives. Initially,Twitterautomatically translated URLs longer than twenty-six characters using TinyURL, although it began using bit.ly instead in 2009[13]and later developed its own URL shortening service, t.co.

On 14 August 2009WordPressannounced thewp.meURL shortener for use when referring to any WordPress blog post.[14]In November 2009, shortened links onbit.lywere accessed 2.1 billion times.[15]Around that time,bit.lyandTinyURLwere the most widely used URL-shortening services.[15]

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 thebit.lyshortener, and questioning whether other shortening services could be profitable from URL shortening in the longer term.[16]It resumed for a time,[17]then closed.

The shortest possible long-term URLs were generated by NanoURL from December 2009 until about 2011, associated with thetop-level.to(Tonga) domain, in the formhttp://to./xxxx,wherexxxxrepresents a sequence of random numbers and letters.[18]

On 14 December 2009Googleannounced a service called Google URL Shortener at goo.gl, which originally was only available for use through Google products (such asGoogle ToolbarandFeedBurner)[19]and extensions forGoogle Chrome.[20]On 21 December 2009, Google introduced aYouTubeURL Shortener, youtu.be.[21]From September 2010Google URL Shortenerbecame available via a direct interface. The goo.gl service provides analytics details and a QR code generator.[citation needed]On 30 March 2018Googleannounced that it is "turning down support for goo.gl over the coming weeks and replacing it withFirebase Dynamic Links"(although existing goo.gl links will continue to function).[22]On July 18, 2024, Google announced that existing Google URL shortener URLs will stop working as of August 25, 2025. Google will add an interstitial page to warn users about this starting August 23, 2024.[23]

Advantages

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The main advantage of a short link is its brevity. Depending on the transcription used, it might be more easily communicated and entered without error. To some extent it can obscure the destination of the URL; this may be advantageous, disadvantageous, or irrelevant.

Disadvantages

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Short URLs often circumvent the intended use oftop-level domainsfor indicating the country of origin; domain registration in many countries requires proof of physical presence within that country, although a redirected URL has no such guarantee.

Abuse

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URL shortening may be utilized byspammersor for illicit internet activities. As a result, many have been removed from online registries or shut down by web hosts or internet service providers.

According to Tonic Corporation, the registry for.to domains, it is "very serious about keeping domains spam free" and may remove URL shortening services from their registry if the service is abused.[24]

In addition, "u.nu" made the following announcement upon closing operations:

The last straw came on September 3, 2010, when the server was disconnected without notice by our hosting provider in response to reports of a number of links to child pornography sites. The disconnection of the server caused us serious problems, and to be honest, the level and nature of the abuse has become quite demoralizing. Given the choice between spending time and money to find a different home, or just giving up, the latter won out.[25]

Google's url-shortener discussion group has frequently included messages from frustrated users reporting that specific shortened URLs have been disabled after they were reported as spam.[26]

A study in May 2012 showed that 61% of URL shorteners had shut down (614 of 1002).[27]The most common cause cited was abuse by spammers.

Linkrot

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The convenience offered by URL shortening also introduces potential problems, which have led to criticism of the use of these services. Short URLs, for example, will be subject tolinkrotif the shortening service stops working; all URLs related to the service will become broken. It is a legitimate concern that many existing URL shortening services may not have a sustainable business model in the long term.[15]In late 2009, theInternet Archivestarted the "301 Works" projects,[28]together with twenty collaborating companies (initially), whose short URLs will be preserved by the project.[15]

Transnational law

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Shortened internet links typically useccTLDdomains, and are therefore often under the jurisdiction of a nation other than where the service provider is located.Libya,for instance, exercised its control over the.ly domain in October 2010 to shut down vb.ly for violating Libyan pornography laws. Failure to predict such problems with URL shorteners and investment in URL shortening companies may reflect a lack ofdue diligence.[29]

Blocking and banning

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Some websites prevent short, redirected URLs from being posted.

In April 2009, TinyURL was reported to be blocked inSaudi Arabia.[30]Yahoo! Answersblocks postings that contain TinyURLs,[citation needed]andWikipediadoes not accept links by any URL shortening services in its articles.[31]TheRedditcommunity strongly discourages‍—  and in some subreddits, outright bans‍—  URL shortening services for link submissions, because they disguise the origin domain name and whether the link has previously been submitted to Reddit, and there are few or no legitimate reasons to use link shorteners for Reddit link submissions.[32]

Privacy and security

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A short URL obscures the target address and can be used to redirect to an unexpected site. Examples of this are "rickrolling",and redirecting toshock sites,or to affiliate websites. The short URL can allow blocked URLs to be accessed, bypassing siteblocklists;this facilitates redirection of a user to blocked scam pages or pages containing malware or XSS attacks. TinyURL tries to disable spam-related links from redirecting.[33]ZoneAlarm,however, has warned its users: "TinyURL may be unsafe. This website has been known to distribute spyware." TinyURL countered this problem by offering an option to view a link's destination before using a shortened URL. This ability is installed on the browser via the TinyURL website and requires the use of cookies.[34]A destination preview may also be obtained by prefi xing the word "preview" to the URL of the TinyURL; for example, the destination ofhttps://tinyurl /8kmfpis revealed by enteringhttps://preview.tinyurl /8kmfp.Other URL shortening services provide a similar destination display.[35]Security professionals suggest that users check a short URL's destination before accessing it,[36]following an instance where the shortening service cli.gs was compromised, exposing millions of users to security uncertainties.[37]There are several web applications that can display the destination URL of a shortened URL.[citation needed]

Some URL shortening services filter their links through bad-site screening services such asGoogle Safe Browsing.Many sites that accept user-submitted content block links, however, to certain domains in order to cut down on spam, and for this reason, known URL redirection services are often themselves added to spam blocklists.

Another privacy problem is that many services' shortened URL format is small enough that it is vulnerable to brute-force search. Many people use URL shorteners when they share links to private content, and in fact many web services like Google Maps have offered automatic generation of shortened links for driving directions that reveal personal information like home addresses and sensitive destinations like "clinics for specific diseases (including cancer and mental diseases), addiction treatment centers, abortion providers, correctional and juvenile detention facilities, payday and car-title lenders, gentlemen's clubs, etc."[38][39]

Additional layer of complexity

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Short URLs, although making it easier to access what might otherwise be a very long URL or user-space on an ISP server, add an additional layer of complexity to the process of retrieving web pages. Every access requires more requests (at least one more DNS lookup, though it may be cached, and one more HTTP/HTTPS request), thereby increasing latency, the time taken to access the page, and also the risk of failure, since the shortening service may become unavailable. Another operational limitation of URL shortening services is that browsers do not resend POST bodies when a redirect is encountered. This can be overcome by making the service areverse proxy,or by elaborate schemes involving cookies and buffered POST bodies, but such techniques present security and scaling challenges, and are therefore not used onextranetsor Internet-scale services.[original research?]

Notable services

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Site Company Type Custom URL Comment
bit.ly Bitly general public yes
goo.gl Google general public — Replaced byFDL(uses Bitly[40])
g.co Google internal — Google's link service[41]
ow.ly Hootsuite Media general public yes Now inside the Hootsuite dashboard
t.co Twitter internal — Twitter's link service[42]
TinyURL TinyURL general public yes
w.wiki Wikimedia Foundation internal — Users can generate links to Wikimedia Foundation projects only.
youtu.be YouTube (Alphabet) internal — Announcement of youtu.be Links[43]

Open sourceand commercial scripts are also available for redirecting and shortening links, usually written inPHPas aweb applicationor a plugin for one of the popular applications such asWordPress.Such scripts avoid many issues with shortening services, keep the domain name as part of the shortened link, and can be made private.

See also

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References

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  1. ^Goo.gl Challenges Bit.ly as King of the ShortArchived10 July 2011 at theWayback Machine– New York Times, 14 December 2009
  2. ^Curtis, Sophie (8 August 2014)."Twitter's t.co URL shortener used to spread spam".The Daily Telegraph.Archivedfrom the original on 3 April 2015.Retrieved15 March2015.
  3. ^"t.co links".developer.twitter.Archivedfrom the original on 27 April 2022.Retrieved10 May2022.
  4. ^"g.co".g.co.Archivedfrom the original on 14 January 2019.Retrieved10 May2022.
  5. ^"URL Shortener".shortener.godaddy.Archivedfrom the original on 3 May 2022.Retrieved10 May2022.
  6. ^"Spammers Storm URL Shortening Services".CertMag. 17 August 2009.Archivedfrom the original on 1 November 2019.
  7. ^"#HootSuite Offers Choice of URL Shorteners ~ From Libya to Liechtenstein – HootSuite Social Media Management".Blog.hootsuite.Archivedfrom the original on 14 June 2013.Retrieved20 April2013.
  8. ^Chapman, Stephen (28 August 2012)."How to spy on campaigns of competitors who use URL shorteners".ZDNet.Archivedfrom the original on 2 September 2012.Retrieved10 September2012.
  9. ^Sullivan, Bryan (March 2009)."Protect Your Site With URL Rewriting – A Stateless Approach: Automatically Expiring URLs".Security Briefs.Microsoft MSDN Magazine.Archivedfrom the original on 17 July 2013.Retrieved1 August2013.
  10. ^ US patent 6957224,Nimrod Megiddo and Kevin S. McCurley; assigned to IBM corp., "Efficient retrieval of uniform resource locators", issued 2005-10-18
  11. ^"Comment thread 8916"Archived5 September 2009 at theWayback Machine.Metafilter.10 June 2001; Announcement of URL shortening service available at makeashorterlink
  12. ^"URL Shortening Services"Archived3 January 2010 at theWayback Machineshortenurl – Supported URL shortening services
  13. ^Wortham, Jenna (7 May 2009)"Bit.ly Eclipses TinyURL on Twitter"Archived23 November 2010 at theWayback MachineBits(blogatThe New York Times). Retrieved 1 January 2011.
  14. ^"WP.me – Shorten Your Links"Archived18 August 2009 at theWayback MachineWordPress.14 August 2009.
  15. ^abcdAhmed, Murad (7 December 2009)."New Project in Scramble To Save Vanishing Internet Links – The Internet Archive Is Fighting To Preserve Shortened Web Links Created by Free Online Services That May Be Running Out of Money"Archived17 December 2013 at theWayback Machine.The Times.Retrieved 1 January 2011.
  16. ^tr.im R.I.P.blog.tr.im
  17. ^tr.im Resurrected.blog.tr.im
  18. ^Michlick, Frank.".TO ccTLD Becomes Worlds Shortest URL Shortener".Domainnamenews. Archived fromthe originalon 3 May 2013.Retrieved20 April2013.
  19. ^Muthusrinivasan, Muthu (14 December 2009)."Making URLs Shorter for Google Toolbar and FeedBurner".Googleblog.blogspot.Archivedfrom the original on 31 May 2013.Retrieved20 April2013.
  20. ^"goo.gl" URL Shortener – Google Chrome Extension Gallery "".Archivedfrom the original on 12 April 2011.Retrieved20 April2013.
  21. ^"Official YouTube Blog: Make Way for youtu.be Links".Official YouTube Blog.Archivedfrom the original on 25 December 2009.Retrieved24 December2009.
  22. ^Hermanto, Michael."Transitioning Google URL Shortener to Firebase Dynamic Links".Google Developers.Archivedfrom the original on 30 June 2018.Retrieved1 April2018.
  23. ^"Google URL Shortener links will no longer be available".developers.googleblog.Google.Retrieved18 July2024.
  24. ^"Tonic Corporation Frequently asked questions".Tonic.to.Archivedfrom the original on 19 July 2013.Retrieved20 April2013.
  25. ^http://u.nu/unu-discontinued "u.nu:: discontinued."
  26. ^"Google Discussiegroepen".Archivedfrom the original on 8 July 2019.Retrieved20 April2013.
  27. ^"Ultimate list of URL shorteners".Yi.tl. 23 May 2012. Archived fromthe originalon 18 April 2013.Retrieved20 April2013.
  28. ^"301Works.org: Free Software: Download & Streaming: Internet Archive".archive.org.Archivedfrom the original on 1 October 2016.Retrieved19 August2016.
  29. ^Staff writer(14 October 2010)."Law, Politics and Internet Addresses – Tough.ly/Treated – Shortened Web Links Are Convenient, But They Come at a Price".The Economist.Archivedfrom the original on 17 October 2010.Retrieved1 January2010.
  30. ^"TinyURL Blocked in Saudi Arabia".Committee to Protect Bloggers. 16 April 2009.Archivedfrom the original on 19 April 2009.
  31. ^"Spam blacklist".meta.wikimedia.org.Meta, discussion about Wikimedia projects.Archivedfrom the original on 20 March 2017.Retrieved4 November2016.
  32. ^"Rediquette".Archivedfrom the original on 8 February 2017.Retrieved9 February2017.
  33. ^Krebs, Brian(13 June 2006)."Spam Spotted Using TinyURL".Security Fixes(blogatThe Washington Post). Retrieved 1 January 2011.
  34. ^"Preview a TinyURL".Tinyurl.Archivedfrom the original on 20 April 2013.Retrieved20 April2013.
  35. ^"the JoshMeister on Security: How to Preview Shortened URLs (TinyURL, bit.ly, is.gd, and more)".Security.thejoshmeister. 11 April 2009.Archivedfrom the original on 25 March 2014.Retrieved20 April2013.
  36. ^University, Carnegie Mellon."Shortened URL Security - Information Security Office - Computing Services - Carnegie Mellon University".cmu.edu.Archivedfrom the original on 1 June 2022.Retrieved26 July2022.
  37. ^"Updated: Cligs Got Hacked – Restoration from Backup Started"BlogatCli.gs(16 June 2009).
  38. ^"Shmatikov, Vitaly," Gone In Six Characters: Short URLs Considered Harmful for Cloud Services. "Blog entry dated April 14, 2016; retrieved April 26, 2016".14 April 2016.Archivedfrom the original on 23 April 2016.Retrieved26 April2016.
  39. ^Georgiev, Martin; Shmatikov, Vitaly (2016). "Gone in Six Characters: Short URLs Considered Harmful for Cloud Services".arXiv:1604.02734v1[cs.CR].
  40. ^"Firebase Extensions | Shorten URLs".Firebase.Archivedfrom the original on 25 September 2020.Retrieved8 September2020.Shortens URLs written to a specified Cloud Firestore collection (uses Bitly).
  41. ^Alexia Tsotsis (18 July 2011)."Google Buys G.Co To Create An Official URL Shortcut For Google Products".Tech Crunch.Archivedfrom the original on 21 July 2011.Retrieved18 July2011.
  42. ^"About Twitter's link service (http://t.co)".Archivedfrom the original on 2 April 2023.Retrieved20 September2021.
  43. ^"Make Way for youtu.be Links".Archivedfrom the original on 21 September 2021.Retrieved19 September2021.
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