payment of back royalties from the $7m/year in revenue generated by the domain. While attempts to repatriate top-level domains are not uncommon, this one is notable in that it cites consumer and human rights violations of the OECD's 2011 Guidelines for Multinational Enterprises rather than multistakeholder representation under ICANN policy, and because the .io domain has enjoyed commercial success, particularly among cryptocurrency companies, with more than 270,000 domains registered. Registration and restrictions Individuals and organisations are allowed to register .io domains. Labels for .io domains may only contain alphanumeric characters and hyphens, and must be between 3 and 63 characters long. Domain names cannot begin or end with a hyphen symbol, and may not contain two consecutive hyphens. The entire domain name may not contain more than 253 characters. Applicants for the registration of .io domains do not need to be registered or established in the British Indian Ocean Territory. Third-level domains, such as "xyz.com.io", can only be registered by an inhabitant of the area. (Since there are no legal, permanent inhabitants of the British Indian Ocean Territory, theoretically no third-level domains will be registered.) Any second-level domains used by NIC.IO and top-level domains cannot be used as a third-level domain. For example, the domains "com.com.io", "org.com.io", and "biz.com.io" are all restricted. Domain names in .io may not be used, "for any purpose that is sexual or pornographic or that is against the statutory laws of any nation." If this requirement is breached, "NIC.IO reserves the right to immediately deactivate the offending registration." .io domains may be registered for a minimum of one year, and a maximum of 5 years. Domain names in .io are priced higher than those in many other TLDs. Registering an available .io-domain currently () costs US$90 per year. Usage The .io domain is used almost exclusively for purposes unrelated to the British Indian Ocean Territory. In computer science, "IO" or "I/O" is commonly used as an abbreviation for input/output, which makes the .io domain desirable for services that want to be associated with technology. .io domains are often used for open source projects, application programming interfaces ("APIs"), startup companies, browser games, and other online services. The TLD is also used for domain hacks, as the letters "io" are an ending of many English terms. For example, Rub.io is a shortened URL that was used for the 2016 U.S. presidential campaign of Marco Rubio. One reason