Casinos detect card counters through a combination of monitoring betting patterns, player behavior, and surveillance. They watch for irregular betting, such as sudden increases after favorable cards, which is a common sign of card counting. Casinos also track how players engage with the game, noting behaviors like excessive focus or changes in betting style, which can raise suspicion. Surveillance cameras and floor staff are trained to spot these patterns, and some casinos use continuous shuffling machines to make it harder for counters to gain an advantage. Additionally, casinos track player activity over time and may flag suspicious accounts based on their betting history. If a player consistently exhibits signs of card counting, they may be asked to leave or banned from the casino.