A domain hack is a domain name that suggests a word, phrase, or name when concatenating two or more adjacent levels of that domain. For example, http://bir.ds/ and http://examp.le/, using the fictitious country-code domains .ds and .le, suggest the word birds and example respectively. In this context, the word hack denotes a clever trick (as in programming), not an exploit or break-in (as in security).
Domain hacks offer the ability to produce short domain names. This makes them potentially valuable as redirectors, pastebins, base domains from which to delegate subdomains and URL shortening services.
On November 23, 1992, inter.net was registered. In the 1990s, several hostnames ending in "pla.net" were active. The concept of spelling out a phrase with the parts of a hostname to form a domain hack became well established. On Friday, May 3, 2002, icio.us was registered to create del.icio.us.
On January 14, 2004, the Christmas Island Internet Administration revoked .cx domain registration for shock site goatse.cx, a domain which used "se.cx" to form the word "sex". The domain was originally registered in 1999. Similar names had been used for parody sites such as oralse.cx or analse.cx; in some cases, .cz (Czech Republic) or .kz (Kazakhstan) are substituted for .cx.
The term domain hack was coined by Matthew Doucette on November 3, 2004 to mean "an unconventional domain name that uses parts other than the SLD (second level domain) or third level domain to create the title of the domain name."
On 11 September 2007, name servers for .me were delegated by IANA to the Government of Montenegro, with a two-year transition period for existing .yu names to be transferred to .me. One of the first steps taken in deploying .me online was to create .its.me as a domain space for personal sites. Many potential domain hacks, such as love.me and buy.me, were held back by the registry as premium names for later auction. One .me domain hack example is please.do.not.disturb.me.
In March 2010, National Public Radio launched its own URL shortener under the domain n.pr using the ccTLD of Puerto Rico. The n.pr domain is currently used to link to an NPR story page by its ID and is one of the shortest possible domain hacks.
In late 2010, Apple launched a URL shortener at the domain itun.es, using the ccTLD of Spain, in a similar move to Google's goo.gl. Unlike goo.gl, which is public and can be used for any web address, itun.es is used only for iTunes Ping URL shortening.
In most cases, registration of these short domain names relies on the use of country code domains, each of which has a unique two-letter identifier.
For example, blo.gs makes use of the top-level domain (TLD) .gs (South Georgia and the South Sandwich Islands) to spell "blogs", fa.st makes use of the TLD .st (São Tomé and Príncipe) to spell "fast", chronolo.gy uses the TLD .gy (Guyana) to spell "chronology", Instagr.am makes use of the TLD .am (Armenia) to spell the name of photo-sharing service "Instagram", helpmelearn.it makes use of the TLD .it (Italy) to spell "help me learn it", sexyi.am uses TLD .am (Armenia) and darkvir.us uses TLD .us (United States) and sharing it for subdomains with free hosting, and tel.ly uses the TLD .ly (Libya) to spell "telly" (a popular British colloquial term for television).
The third-level domains del.icio.us, cr.yp.to and e.xplo.it make use of the SLDs icio.us, yp.to and xplo.it from the TLDs .us (United States), .to (Tonga) and .it (Italy) to spell "delicious", "crypto" and "exploit" respectively.
In some cases, an entire country code domain has been re-purposed in its international marketing, such as .am (Armenia), .fm (Federated States of Micronesia), .cd (Democratic Republic of the Congo), .dj (Djibouti), and .tv (Tuvalu) for sites delivering various forms of audiovisual content.
Since the introduction of .eu domains (eu meaning "I" in Romanian and in Portuguese), these domains have become popular in Romania, with people registering their names with the .eu extension.
In French, Italian and Portuguese, « là » or « lá » mean "there". As the .la domain (Laos) is available for second-level registration worldwide, this can be an easy way to get a short, catchy name like "go there". In Italy some TLDs are identical to Italian Provinces' identifier, such as .to (Turin) or .tv (Treviso) and are thus extensively used for web domains in the area. The Canadian domain .ca is also trivial to use as « cá » ("here") in Portuguese or « ça » ("that") in Canadian French; local Canadian presence is required.
A fad amongst French-speakers was to register their names in the Niue TLD .nu, which in French and Portuguese means "nude" or "naked"; however, as of 2007[update], Niue authorities have revoked many of these domain names. The handful that remain are joke domains without actual nudity. French speakers often use the Jersey TLD .je, since "je" means "I" in French. In addition, .je is used in the Netherlands, as it can mean both "you" or "your", and "small", since the addition of -je to most nouns produces a colloquial diminutive for (e.g. huis.je, or the well known iPhone app feest.je (feestje meaning "party").
Likewise, Dutch, Swedish, and Danish speakers sometimes use .nu, because it means "now" in these languages. The TLD is still used by many Swedish sites, as prior to 2003 it was impossible for individuals (and difficult for organizations) to register arbitrary domains under the .se TLD.
In Russian, net (as «nyet») means "no", so there are many domains in the format "something.net" (e.g. redaktora.net meaning "no editor"). A similar use of .info (in many languages where the term signifies "information") is to use a negatory term and .info to yield local equivalents to "there is no information".
In Czech, Polish and Slovak, to means "it", so there are many domains using Tonga's .to in the format "do-something.to" (e.g., zrobie.to, meaning "I will do it" in the Polish language or prestahujeme.to meaning "We will move it" as Slovak moving service). Notably, Czech file sharing service uloz.to was founded in 2007, and its name "ulož to" means "save it".
In Slovenian, si is a dative form of the reciprocal personal pronoun and a second person form of the verb to be. As .si is a Slovenian ccTLD, domain hacks are abundant. Additionally, the domain is attractive to speakers of Romance languages, because it is a conjunction, pronoun or an affirmative interjection in many. ARNES limits the use of the domain to residents and entities of Slovenia.