Online ticket brokering is the resale of tickets through a web-based ticket brokering service. Prices on ticket brokering websites are determined by demand, availability, and the ticket reseller. Tickets sold through an online ticket brokering service may or may not be authorized by the official seller. Generally, the majority of trading on ticket brokering websites concerns itself with tickets to live entertainment events whereby the primary officially licensed seller's supply has been exhausted and the event has been declared "sold-out". Critics of the industry compare the resale of tickets online to ‘ticket touting’, ‘scalping’ or a variety of other terms for the unofficial sale of tickets directly outside the venue of an event.