Card Counting
Card counting is a legal blackjack technique that tracks whether the cards left to be dealt favor the player or the dealer. It does not tell you the next card. It tells you when the odds have shifted enough to bet more, and by how much.
Short answer
Card counting works because a shoe rich in high cards (tens and aces) favors the player and a shoe rich in low cards favors the dealer. A counting system assigns a value to each card so you can keep one running number as the cards come out. When that number, adjusted for how many cards are left, is high, you bet more and sometimes change how you play the hand. When it is low, you bet the minimum. In our own simulation a flat bettor faces a 0.47% house edge, but a modest bet spread tied to the count moves that to roughly a +0.29% player edge. The margin is small, and it only shows up over a long grind.
The guide
Common questions
Is card counting illegal?
No. Using your brain to track cards is not cheating and is not illegal in the United States. Casinos are private businesses and can ask a suspected counter to stop playing blackjack or to leave, so counters use bet sizing and behavior to avoid drawing attention.
Do you need a photographic memory?
No. You do not memorize cards. You keep a single running number that goes up and down as cards appear, then divide by the decks remaining. The math is addition, subtraction, and one division.
Can you count cards online?
Against a standard live shoe, yes in principle, but most online blackjack shuffles after every hand or uses a continuous shuffling machine, which removes the memory the count depends on. Counting only works when the same cards stay out of play until a shuffle.
How long does it take to learn?
Recognizing values and keeping a running count can come in days. Doing it fast, under table pressure, with correct betting and deviations, takes sustained practice. That is what the trainer is for.