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TLD and gTLD: Top Level Domain

Last Edit: 28/03/17

TLD stands for Top Level Domain and gTLD stands for Generic Top Level Domain. Domain names are part of the Domain Name System (DNS): which simple put, are alphanumeric names that make it easier for Internet users to locate a resource found on the Internet (at an IP address). The Domain Name System was launched in 1984, and the first com domain names were registered in 1985-1986; some of the earliest domain names registered were, and In the mid to late 1980's, the backbone networks of the Internet were controlled by Federal academic agencies like the National Science Foundation. Commercial access and access for the general public was restricted; therefore, the number of individuals and businesses registering domain names was low. During the mid 1980's, there was only a handful of Top Level Domain extensions; the first five were:

  1. com - commercial use.
  2. net - for Internet service providers.
  3. org - for noncommercial organisations.
  4. mil - military departments of the United States government.
  5. gov - agencies of the United States government.

When commercial access to the Internet was implemented - 1990-1995 - commercial Internet Service Providers formed the backbone of the Internet and the general public started to gain unlimited access. Alongside this interest, was an interest in registering domain names - for businesses and personal use - so that end-users could provide a service online with a unique identity. The problem was the lack of domain names available due to the lack of extensions on offer. ICANN - who manages the Domain Name System (DNS) - has slowly expanded the number of Top Level Domain extensions, and the original Top Level Domain extensions were categorised as Generic Top Level Domains - to take into account code Top-Level Domains. Each Top Level Domain is assigned an organisation to manage the domain; management of a Top Level Domain includes running the authoritative nameserver for the domain and assigning registrars who can register and manage Second Level Domains (such as example in com) for end users. The organisations who manage Top Level Domains are assigned by ICANN. There are currently over 1000 Top Level Domains, some of the most popular Generic Top Level Domains are listed below, but only comprise a snippet of the full list of TLDs:

The types of Top Level Domains that are categorised by IANA are as follows:

  1. ARPA - infrastructure top-level domain
  2. gTLD - generic top-level domains
  3. grTLD - restricted generic top-level domains
  4. ccTLD - country code top-level domains (ac and zw)
  5. IDNs - internationalized top-level domains
  6. sTLD - sponsored top-level domains
  7. tTLD - test top-level domains