|TLD type||Country code top-level domain|
|Registry||nic.yu (Yugoslav Internet Domain Registry)|
|Intended use||Entities connected with former Yugoslavia|
|Actual use||Expired in March 2010|
|Registration restrictions||Registration not available since 10 March 2008.|
|Structure||Registrations were made at third level beneath established subdomains|
.yu was the Internet country code top-level domain (ccTLD) that was assigned to Yugoslavia and was mainly used by the Federal Republic of Yugoslavia and its successor Serbia and Montenegro between 1994 and 2010.
.yu is the most heavily used top-level domain ever to be deleted.
The .yu ccTLD was assigned originally to the Socialist Federal Republic of Yugoslavia, during the government project for the development of scientific-technological information (SNTIJ). The official registrants were the University of Maribor and the Jožef Stefan Institute, which were located in Slovenia.
After the Yugoslav wars broke out, SFR Yugoslavia dissolved and the Federal Republic of Yugoslavia was formed, but was under international sanctions at the time. The .yu domain registry had been left in Slovenia, and the domain became a succession matter when the Slovenians refused to relinquish the domain name to the University of Belgrade in Serbia, which had requested they do so.
In 1994, the Internet Assigned Numbers Authority finally decreed that the domain should pass to FR Yugoslavia. Since then the domain was managed by the YUNET Association, an organization based in the Faculty of Electrical Engineering at the University of Belgrade.
FR Yugoslavia renamed itself Serbia and Montenegro in February 2003. The code YU was replaced by CS in July 2003 following the official name change, and the ccTLD .cs was reserved for Serbia and Montenegro after the name change. However, .cs was never actually used, and .yu remained one of the few ccTLDs that did not correspond to a current ISO 3166-1 two-letter code.
The state union of Serbia and Montenegro was dissolved in July 2006, and in September 2006, ISO accordingly proposed the replacement the codes RS for Serbia and ME for Montenegro. On 26 September 2006 the ISO 3166 Maintenance Agency agreed on the change of ISO 3166-1 Alpha-2 code CS to RS. The new domains .rs for Serbia and .me for Montenegro became active shortly thereafter.
In September 2007 ICANN resolved that the .yu domain would be operated temporarily under the Serbian National Register of Internet Domain Names, operators of the new .rs domain registry. A two-year transition period started, and the .yu domain was scheduled to expire on 30 September 2009. However, the Serbian registrar requested an extension and ICANN decided to extend the transition deadline another six months away. Finally, the Serbian registrar declared the end of the .yu domain at 12:00 CEST on 30 March 2010.
Former use of .yu domains 
All of the domains directly under .yu were reserved for legal entities only. Top level domain was reserved for federal institutions and official governmental institutions, as well as Internet service providers. The Serbian Orthodox Church was also allowed to use .yu domain.
The second-level domains under .yu included:
- Academic organizations, such as universities, were registered under the academic domain, .ac.yu. For example, the School of Electrical Engineering (.etf) at the University of Belgrade (.bg) had the etf.bg.ac.yu domain.
- Educational institutions, such as primary and high schools, used the .edu.yu domain.
- Independent organizations used the .org.yu domain.
- Corporations used the .co.yu domain.
- Government used the .gov.yu domain.
Montenegrin websites often used subdomain .cg.yu which was given for free to customers of a Montenegrin ISP which registered the domain, making it a popular option for those who opt not to register a domain for their website.
See also 
- "The Serbian National Register of Internet Domain Names Home Page". RNIDS. Archived from the original on 01 February 2010. Retrieved 30 March 2010.
- Preliminary Report for Special Meeting of the ICANN Board of Directors ICANN, 11 September 2007
- "Preliminary Report of Special Board Meeting". ICANN. 30 September 2009. Archived from the original on 15 October 2009. Retrieved 13 October 2009.
- "End in sight for Yugoslav domains". BBC News. 29 September 2009. Archived from the original on 29 September 2009. Retrieved 29 September 2009.
- IANA .yu whois information
- "Srbija i Crna Gora - koje će biti ime domena? Internet domen Srbije: RS, SS, SP, SQ, SW ili SX", Elitesecurity, 5 February 2003. (Serbian)