A whitelist is a list of entities approved for authorized access or privileged membership to enter a specific area in the computing world. These entities could include electronic groups or organizations, privileged websites or even email addresses. Whitelist may also refer to an actionable promotion or recognition of an organization, group or individual. This term may also be known as an approved list. A whitelist ICO means that you have to register in advance to participate in the ICOs, which are usually hallmarks of popular ICOs that have a limited number of coins to offer.