Online poker is the game of poker played over the Internet. It has been partly responsible for a dramatic increase in the number of poker players worldwide. Christiansen Capital Advisors stated online poker revenues grew from $82.7 million in 2001 to $2.4 billion in 2005, while a survey carried out by DrKW and Global Betting and Gaming Consultants asserted online poker revenues in 2004 were at $1.4bn.

Overview

Traditional (or "brick and mortar", B&M, live) venues for playing poker, such as casinos and poker rooms, may be intimidating for novice players and are often located in geographically disparate locations. Also, brick and mortar casinos are reluctant to promote poker because it is difficult for them to profit from it. Though the rake, or time charge, of traditional casinos is often high, the opportunity costs of running a poker room are even higher. Brick and mortar casinos often make much more money by removing poker rooms and adding more slot machines.

Online venues, by contrast, are dramatically cheaper because they have much smaller overhead costs. For example, adding another table does not take up valuable space like it would for a brick and mortar casino. Online poker rooms also allow the players to play for low stakes (as low as 2¢) and often offer poker freeroll tournaments (where there is no entry fee), attracting beginners.

Online venues may be more vulnerable to certain types of fraud, especially collusion between players. However, they have collusion detection abilities that do not exist in brick and mortar casinos. For example, online poker room security employees can look at the hand history of the cards previously played by any player on the site, making patterns of behavior easier to detect than in a casino where colluding players can simply fold their hands without anyone ever knowing the strength of their holding. Online poker rooms also check players' IP addresses in order to prevent players at the same household or at known open proxy servers from playing on the same tables.

Free poker online was played as early as the late 1990s in the form of IRC poker. Planet Poker was the first online cardroom to offer real money games. The first real money poker game was dealt on January 1, 1998. Author Mike Caro became the "face" of Planet Poker in October 1999.

The major online poker sites offer varying features to entice new players. One common feature is to offer tournaments called satellites by which the winners gain entry to real-life poker tournaments. It was through one such tournament on PokerStars that Chris Moneymaker won his entry to the 2003 World Series of Poker. He went on to win the main event causing shock in the poker world. The 2004 World Series featured three times as many players as in 2003. At least four players in the WSOP final table won their entry through an online cardroom. Like Moneymaker, 2004 winner Greg "Fossilman" Raymer also won his entry at the PokerStars online cardroom.