According to current IANA policy, the .int gTLD is reserved for international treaty-based organizations, United Nations agencies and organizations or entities having Observer status at the UN. This top-level domain was initially created for use by NATO, to replace the previous .nato TLD.
.int is considered the strictest gTLD in as much as it implies that the holder is a subject of international law. For this reasons, the application procedure requires the applicant to provide evidence that it is indeed treaty-based by providing a United Nations treaty registration number and that it has independent legal existence.
Hence, the Stockholm Convention on Persistent Organic Pollutants (POPs) saw its application for a .int domain rejected on the grounds that the Convention did not explicitely create an entity subject of international law. However, POPS appealed to the IANA Reconsideration Committee and obtained its .int domain on the grounds that other Conventions lacking such specific language had nevertheless obtained a .int registration
Additionally, .int was historically also used for "Internet infrastructure databases". The contents of .arpa had been slated to be moved into .int, but in 2000 the IAB recommended that no new infrastructure databases be added to .int and that .arpa retain its current use. Its last remaining role was for reverse translation of IPv6 addresses under the .ip6.int zone. This zone was officially turned off on 6 June 2006 in favour of .ip6.arpa, also administered by IANA.
The .eu.int sub-domain was used by the European Union-affiliated institutions. However, the aforementioned institutions’ domain names changed to the TLD .eu on May 9, 2006 (Europe Day). The institutions’ previous ".eu.int" addresses will continue to be accessible for a transitional period of at least one year.
A dedicated article offers comprehensive list of these organizations and indicates which ones are actually intergovernmental treaty-based organizations, UN agencies or UN observers, and which ones obtained their .int prior to the establishment of these very strict guidelines.
Several .int domains were granted prior to the application of the strict guidelines described above. YMCA (Young Men's Christian Association) is perhaps the most striking example of the loose guidelines applied in the early 1990s. In spite of the potentially confusing impression given by a .int TLD, IANA has decided not to withdraw the .int assignment from YMCA and other organizations who do not meet the current criteria.