#File extensions list .xz registration

Some institutions, such as the Exploratorium, that do not meet the current registration criteria have grandfathered domain names. This domain is therefore almost exclusively used by American colleges and universities. In the U.S., its use was restricted in 2001 to post-secondary institutions accredited by an agency on the list of nationally recognized accrediting agencies. edu TLD is limited to specific higher educational institutions such as, but not limited to, trade schools and universities. However, a few grandfathered domains do not meet these criteria. int TLD is strictly limited to organizations, offices, and programs endorsed by a treaty between two or more nations. According to RFC 1591 (March 1994) 'This domain is intended to hold only the computers of network providers.'

This is an open TLD any person or entity is permitted to register. Some non-government organizations may fit here.' While mainly non-profits have used this domain, it was never restricted from miscellaneous use.

Originally created as a miscellaneous category as stated in RFC 920 (October 1984) '.any other domains meeting the second level requirements,' and clarified in RFC 1591 (March 1994), 'This domain is intended as the miscellaneous TLD for organizations that didn't fit anywhere else. It was originally administered by the United States Department of Defense. Domain name registrations may be successfully challenged if the holder cannot prove an outside relation justifying reservation of the name, to prevent ' squatting'. Though originally intended for use by for-profit business entities, for a number of reasons it became the main TLD for domain names and is currently used by all types of entities including nonprofits, schools, and private individuals.

DNSSEC: presence of DS records for Domain Name System Security Extensions.

IDN: support for internationalized domain names (IDN).

Seven generic top-level domains were created early in the development of the Internet, and predate the creation of ICANN in 1998.

generic-restricted top-level domains (grTLD).

IANA distinguishes the following groups of top-level domains:

File extensions list .xz