Card counting in blackjack: how it works and why it's pointless in online casinos

The movies love a neat storyline: a player with a fine grasp of math, a good memory, and the ability to add up quickly in their head beats the casino at blackjack over and over with ease. In practice, the point of counting cards is nowhere near that obvious.

How card counting works

First off, card counting isn't an exercise reserved for geniuses: a player doesn't need to memorize exact cards, they just try to keep a running balance of the high and low cards still left in the deck. Here's the gist in a few points.

Cards played in previous hands go to the discard tray and don't take part in the next hand until the dealer shuffles them back in with the rest of the deck. A card counter starts with modest bets and watches for a while, paying attention to the cards that have gone to the discards.

If a lot of low cards have been discarded, the share of high cards in the deck grows — that's a good moment to raise your bets, since your odds of a blackjack go up. For the dealer, plenty of high cards is the opposite: a problem, because they keep drawing until they reach at least 17 and so are more likely to bust. That's why it doesn't matter which exact card was discarded — the queen of spades or the jack of hearts: you just need to remember that a high one, or a low one, is gone.

How to track discarded cards effortlessly

You don't have to memorize them at all — use the Hi-Lo method, counting points for the cards heading to the discards. The larger the positive total, the more it makes sense to raise your bets: the remaining cards are rich in tens and aces, so naturals and strong hands come more often. In a multi-deck shoe, size your bets by the true count rather than the running one: divide the running total by the number of decks still to be dealt. If the count is negative, it means low cards dominate the deck — you should step away, or at least keep your bets small.

How the random number generator kills the point of counting

The whole idea of counting is that the ratio of high to low cards in the deck shifts after each hand, affecting your odds. But RNG blackjack sends cards to the discards only for show: in reality the algorithm starts every hand as if it were the first, with a full set of cards. That's why counting cards in RNG blackjack is pointless.

How live casinos fight card counting

Even though a live casino has a real dealer, the house has no interest in improving a customer's odds there either. The countermeasures against the 'math types' are simple. A plastic cut card is inserted partway into the shoe in advance: once the dealer reaches it, the shoe is finished and all the cards are shuffled together, so the cards behind the cut card are never dealt and the count has limited room to build up. Some tables go further and use a continuous shuffling machine: the dealer puts used cards straight back into the machine instead of a discard tray, so every hand is effectively dealt from a full set of cards and counting becomes impossible.

Online casinos also analyze a customer's behavior patterns, noting when they raise and when they lower their bet, and can ask the dealer to shuffle immediately — or even force the player away from the table.

Takeaway

Card counting really was successful, but first and foremost in the land-based casinos of the last century, when it was relatively new. Modern online casinos worked out countermeasures long ago and rely on technical tools, so you won't outfox the house this way.