How Casinos Catch Card Counters and What They Do About It

Blackjack is a popular casino game where the goal is to try and get a hand total as close to 21 as possible, without going over. 

It’s one of the few games that combines decision-making with chance, which means some players might try to gain an edge by tracking which cards have been played. This method is known as card counting.

In this blog, we’ll explain exactly what card counting is, how it works, and why some people may try to use it in games of blackjack. We’ll also look at how casinos can recognise when someone may be counting cards, and what actions they might take when they suspect it’s happening. You’ll also learn whether card counting is against the law, whether it works online, and why trying it may not be worth your time.

If you’ve ever wondered how casinos protect their games, or what happens behind the scenes when they suspect unfair play, this blog will help you understand. You’ll also get a better idea of how blackjack works and why gambling responsibly is so important.

What Is Card Counting?

Card counting is a method some people use to try and estimate whether the next hand in a game of blackjack might be more favourable to the player, or the dealer. It involves keeping track of which cards have already been dealt from the shoe (the stack of cards used in the game), in the hope of predicting which cards might come next.

Blackjack is played using one or more standard decks of 52 cards. Depending on the casino or the game rules, there could be anything from one to eight decks in use. The aim of the game is to try and get a hand total as close as possible to 21 without going over, while having a higher total than the dealer. 

Each card has a value: number cards are worth their face value, picture cards (Jack, Queen and King) are worth 10, and Aces can count as either 1 or 11.

Card counting doesn’t involve memorising every single card. Instead, it uses a scoring system to give a rough idea of how many high or low cards may be left in the shoe. High cards, like tens and Aces, are often seen as better for the player, while low cards may favour the dealer. One of the most basic systems is the Hi-Lo method. In this system:

• Low cards (2 to 6) are given a value of +1
  
• Middle cards (7 to 9) are counted as 0
  
• High cards (10, Jack, Queen, King, Ace) are counted as -1

The player keeps a running total, or “count”, in their head. If the count goes up, it means more low cards have been played, so high cards are likely to be left in the deck. If the count goes down, more high cards may have already been used.

It’s worth pointing out that card counting doesn’t guarantee anything. Blackjack is still a game of chance. Cards are shuffled, the dealer’s actions are fixed by house rules, and players do not have any way of knowing exactly what will be dealt next. Even experienced card counters can lose money over time. Gambling should never be viewed as a way to make money or gain an advantage.

The impact of card counting also depends on the game setup. In many UK land-based casinos, automatic shuffling machines are often used. These shuffle the cards continuously, which makes card counting far less effective. Some games may also use multiple decks or re-shuffle after a set number of hands, both of which make it more difficult to keep track of the cards.

Online blackjack games, especially those using Random Number Generators (RNGs), re-shuffle the virtual deck after each hand. That means counting cards doesn’t apply in these games. Some live dealer tables may use real decks, but most will shuffle regularly or follow strict procedures that limit any potential card tracking.

As with all forms of gambling, the outcome in blackjack is never certain. Every hand you play involves risk. If you’re thinking about trying this game, it can help to read the rules first and check the paytable, as different tables may have slightly different house rules, minimum bets or potential payout structures.

If you choose to play blackjack or any casino game, it’s important to gamble safely. Set limits, know your budget, and take regular breaks. If you ever feel gambling is becoming a problem, help and support is available through organisations such as BeGambleAware.org or GamCare.

Is Card Counting Illegal?

Card counting is not illegal in the United Kingdom. You’re allowed to use your memory and mental maths while playing blackjack. 

However, land-based casinos are private venues, which means they can choose who they allow to play. If a casino manager or member of staff thinks your style of play could reduce the casino’s usual advantage— they can ask you to stop playing or leave the table. This is allowed under the Gambling Act 2005.

The UK Gambling Commission (UKGC) does not consider card counting to be cheating, as long as you’re not using any devices, apps or outside help. It’s based purely on observation and mental calculations, which are not against the rules—but that doesn’t mean casinos will allow it to continue if they notice it happening.

How Do Casinos Catch Card Counters?

Casinos pay close attention to blackjack tables because card counting, if done effectively, can reduce the house edge—which is the built-in advantage the casino has over players. 

In a typical UK blackjack game using six decks, the house edge can be as low as 0.5%, but only if the player follows an optimal basic strategy for every hand. This means making the statistically best decision for every possible card combination. Most players don’t play with perfect accuracy, so in reality, the house edge is often higher—sometimes noticeably so.

Because card counters try to reduce this edge even further, casinos use various tools to detect it. If someone is able to shift the odds in their favour—even slightly over time—the casino may lose more than expected, which is why they actively look out for this behaviour.

Here are some of the key methods used to spot card counting:

• Bet-spread monitoring: This involves tracking how much a player is betting during each hand. If someone consistently bets low, and suddenly raises their stakes when the shoe reaches a certain point, it may suggest they believe the remaining cards may be more favourable. For example, jumping from £5 to £100 in a short time can trigger a review.
  
• Surveillance cameras: High-quality cameras watch over every table. These record how players behave, how chips are moved, and how cards are played. Security teams can analyse this footage to try and identify any patterns that match known card counting techniques.
  
• Player-tracking systems: Many players use loyalty cards to collect points or perks, depending on the casino. These cards also help casinos track your play, including how often you bet, how much you wager, and how your results compare to expectations. If a player’s results appear unusually consistent or profitable, it may lead to further scrutiny.
  
• Behavioural cues: Trained staff also look for behaviours that don’t match typical playing styles. This might include avoiding conversation, frequently changing tables, or discreetly signalling to others nearby. These signs don’t prove anything by themselves, but may prompt a closer look.
  
• Table exits and shuffle timing: Some card counters leave the table when a new shoe is introduced because they no longer have any useful information about the card order. Casinos often take note of any players who regularly walk away at this point.

Casinos combine technology and staff training to protect the balance of their games. While blackjack relies on chance, players using advanced techniques to influence outcomes—especially when the edge is already low for those using basic strategy—can impact the game’s long-term fairness. That’s why casinos take these steps to identify and address card counting early.

What Do Casinos Do To Card Counters?

If a casino believes you’re counting cards, they may take action in a series of steps, depending on how confident they are and how you’re affecting the game.

1. Polite chat – A floor supervisor may engage you to try and break concentration, or remind you of house conditions.
   
2. Rule changes – The dealer could be told to shuffle earlier, often called a “heat shuffle”, which removes any favourable deck composition.
   
3. Game refusal – If the casino suspects card counting, management might take steps to limit any possible advantage. This could include asking you to move to a different table, changing the game to use an automatic shuffling machine, or, in some cases, asking the dealer to stop dealing blackjack at that table for the time being.
   
4. Exclusion – Under the terms of entry, the venue can ban you for a period or permanently. Your name and image may be shared across the operator’s other UK sites.

Does Card Counting Work Online?

For standard RNG (Random Number Generator) blackjack, no. 

The virtual deck is re-shuffled after every hand by certified software, giving each deal independent odds. Live-dealer tables stream real cards, yet nearly all UK providers use either:

• Continuous shuffling machines (CSMs), which feed used cards straight back into the shoe, or
  
• Frequent manual shuffles, typically after 50% of the shoe is dealt.

Both practices usually reset the composition too quickly for any running count to gain a statistical edge.

Why You Shouldn’t Try To Count Cards

Card counting is legal, but it’s rarely practical or worthwhile—especially when you consider the effort involved and the possible consequences if you’re caught. 

Here’s why it may not be a good idea:

• Hard to do well – Counting cards accurately in a live casino is difficult. You’ll need to concentrate constantly while managing chips and decisions across multiple decks. A single mistake can remove any small edge.
  
• Limited benefit – Even skilled counters may only improve expected returns by around 1%. On a £10 bet, that’s about 10p per hand—often wiped out by natural variation or incorrect play.
  
• Casinos are prepared – Early shuffles, betting restrictions, and automatic shufflers are used to block counting attempts before they become effective.
  
• Tiring and stressful – Keeping track of cards over long sessions takes the enjoyment out of the game for many players.
  
• You could be stopped – If staff suspect you’re counting, they may ask you to leave the table, refuse further play, or in some cases, ask you to leave the premises entirely. Some casinos may even share your details with their other venues.

Blackjack involves chance, and no strategy can remove that. Gambling should always be approached responsibly, with limits and awareness of the risks.