Keno is offered in both physical and online lotteries and casinos. Some state lotteries also offer the game. In the US, for instance, players can enjoy Keno in 16 states (as of 2017). These include Ohio, Maryland, Michigan, Georgia, Kansas, and Washington among others.
Players can walk into these providers' premises and buy physical Keno tickets. However, this article focuses more on how to play Keno. Most of these physical lotteries and state lotteries have online versions where players can buy tickets from their websites. An online lottery ticket holds just as much power as a physical one. In Australia, there is a website that is dedicated to Keno only.
The beauty of an online lottery is that one can buy an online lottery ticket even when they are away from the lottery's region. Care should be taken with state lotteries, however. Some of them have tough regulations on winnings by outsiders. E.g. punitive taxes on winnings.