How casinos detect card counters

Even people who’ve never stepped foot in a casino, or visited an online casino, will have probably heard of card counting. It’s a strategy where a player keeps track of which cards have already been played in a game of blackjack, so they have a better idea of what’s still left in the deck. The main goal is to figure out the odds, based on what’s likely to come up next, and adjust their bets to take advantage of it.

Many people think of card counters as geniuses pulling off an incredible math trick, but that’s not entirely true, although it does take a lot of focus, memory, and practice. The problem is, card counting is seen as a way to tip the odds (albeit slightly) in the player’s favor. That not only spells bad news for the casino due to potential losses, but also affects the experience of other players if things get heated at the table. 

How Do Card Counters Get Caught?

Since card counters have been an issue for decades, casinos have become incredibly vigilant when it comes to spotting a player who’s counting.

The House Is Always Watching

The first line of defense is the staff working the floor. Dealers and pit bosses aren’t just there to deal the cards—they’re trained to notice anything out of the ordinary. For instance, they may watch how players react to certain cards and how people vary their bets in seemingly unusual patterns.

Every bet a player makes can be analyzed against the cards dealt, and if that pattern starts to look like something a skilled card counter would do, the alarm bells start ringing—figuratively, of course.

Another giveaway is when a player suddenly increases their bet tenfold at just the right moment. For example, if a player always raises their bet when they know the deck is full of high cards, but lowers the bet when the deck is stacked with low cards, the pattern gets harder to hide the longer they do it.

Many card counters may not even realize they’re being watched, but if a staff member catches even the slightest whiff of suspicious play, they’ll inform the pit boss and flag the player to the team monitoring the security feeds.

Cameras and Recognition Software

And speaking of cameras, there isn’t a single corner of a casino that isn’t being recorded. Not only does this protect the casino from theft, fraud, or allegations, but it’s also used to zoom in on a player’s cards, chips, and even facial expressions that could give a card counter away. If the playing style raises red flags, they’ll simply roll back the tape and have their own expert counter break down the strategy.

One step further, facial recognition software has been introduced in some of the largest casinos, which can detect the face of a card counter who has already been identified on a shared database. This means if you get caught doing it in one casino, there’s a likelihood that the next one you walk into will already have you in their sights.

The Casino ‘Black Book’

Another method of identifying a card counter, as well as people who cheat or consistently win at a table, is the ‘Black Book.’ These are essentially lists of people that staff want to keep an eye on. Many casinos share their Black Books through a gaming control board, which is government-regulated. This means those who end up on the list will get extra attention when entering a casino — or worse, get asked to leave before they even get their chips.

Word Travels

It’s easy to think that all frowned-upon techniques are caught in 4K, or by eagle-eyed dealers and other floor staff — but that’s not always the case! Oftentimes, card counters are outed by other players who recognize someone from another casino known to win big, or who simply notice the patterns of a counter and report them. 

An important aspect for casinos is having open communication, especially when it comes to individuals who might make the business look bad. Once someone’s on the radar, word can spread pretty fast. In fact, a casual comment about someone, or even a joke about being a counter, is enough to attract the attention of the surveillance team. 

Card Counting in Online Casino

Card counting is rendered useless when it comes to online casino games, as the whole setup is different from playing inside a physical casino. For example, ‘Random Number Generators’ shuffle the cards after every hand to ensure it’s fair, making card counting impossible. 

Platforms that offer live casino games, like PokerStars and other popular sites, also make card counting almost impossible, but are still monitored. They keep an eye out for tell-tale betting patterns and the frequency of big wins. Automated systems also run in the background to track a player’s activity, looking at a particular strategy, win rates, or setting unusual betting limits that could give them an unfair advantage. Some sites even have continuous shuffling machines or shuffle more often during live casino games, to throw a count off. 

Is Card Counting Illegal?

So, after hearing all the lengths casinos go to in order to catch card counters red-handed, many assume it’s a crime. But the truth is, it’s totally legal in the UK and the U.S., as long as you’re doing it in your head and not using equipment to help determine the odds or influence your bets.

That being said, casinos don’t like it one bit. And even though it’s not technically considered cheating, it’s still seen as a way to get an edge over the house, which could cost them big. Since casinos are often privately owned businesses, they can refuse service to anyone they want, or even ban them altogether!

Casinos know they can’t stop every clever player using strategies they think will improve their odds, but they actively watch for card counters to avoid huge losses. So next time you see someone winning big, don’t be surprised if they start getting more attention than usual — they’re just trying to rule them out as a potential card counter.