Why Card Counting Doesn't Work Online (And What Casinos Do Instead)

I get asked this question constantly: "Can I use your calculator to beat online blackjack?"

The short answer is no. The longer answer explains why—and understanding this will save you money and help you appreciate what makes physical casinos different.

The Core Principle of Card Counting

Card counting works because of a simple fact: cards that have been dealt cannot be dealt again until the shoe is reshuffled.

In a physical casino with a 6-deck shoe, if you've seen twenty 10-value cards come out in the first two decks, you know the remaining four decks are relatively poor in 10s. Conversely, if you've seen very few 10s, the remaining shoe is rich in them—and that's when you have an edge.

This is called deck depletion, and it's the entire foundation of advantage play.

How Online Blackjack Destroys This

Online casinos use one of two methods, both of which eliminate deck depletion entirely:

Method 1: Shuffle After Every Hand

Most online blackjack games shuffle the virtual deck after every single hand. You can verify this by reading the game rules (usually hidden in a small "i" button).

What this means mathematically:

• Every hand starts from a fresh, complete shoe
• The composition is always 4/13 ten-value cards (~30.8%)
• Previous hands provide zero information about future hands
• The true count is always effectively zero

There's no memory between hands. You're playing basic strategy against a fixed house edge, forever.

Method 2: Random Number Generators (RNGs)

Even when an online game appears to use a shoe that depletes, the underlying system is typically an RNG that simulates card distribution without actually tracking a finite deck.

Here's a simplified version of how this might work:

def deal_card():
    # This doesn't track what's been dealt
    # Every call is independent
    return random.choice(['2','3','4','5','6','7','8','9','10','J','Q','K','A'])

Each card is drawn from a fresh probability distribution. The "shoe" is theatrical—a visual representation that has no bearing on the actual mathematics.

Some RNG implementations do simulate a finite shoe, but shuffle it continuously in the background, which has the same effect as Method 1.

Live Dealer Games: The Grey Area

"But what about live dealer blackjack? That's a real shoe!"

This is where it gets interesting. Live dealer games do use physical cards dealt from a real shoe. In theory, deck depletion exists.

In practice, casinos have countermeasures:

Penetration limits: Live dealer shoes are typically shuffled after 50% penetration or less. In a 8-deck shoe, you might only see 4 decks before a shuffle. This dramatically reduces the variance—and the counting opportunity.

Bet limits: Online live dealer tables often have tight bet spreads. If the minimum is €10 and maximum is €500, your spread is only 1:50. Professional counters in physical casinos might use 1:20 spreads in high-stakes games. But more importantly, you can't just "wong in" (joining mid-shoe when the count is high) because online tables typically require you to be seated before the shoe starts.

Detection is trivial: Online casinos log every single bet you make. They can run automated analysis looking for bet-count correlation—the same math I discuss in my Excel-to-web post. A human pit boss might miss your 1:8 spread, but software won't.

Session data: They know exactly when you join, when you leave, how long you play. Leaving whenever the count goes negative is a classic tell.

What Casinos Actually Worry About

If online blackjack isn't vulnerable to counting, what are online casinos concerned about?

Bonus abuse: Exploiting sign-up bonuses and promotions with low-variance play. This is a mathematical edge, but it's one-time and casinos have gotten sophisticated at detecting it.

Collusion in poker: Players sharing hole card information across multiple accounts.

Software exploits: Bugs in game logic, timing attacks, or RNG weaknesses. These are rare and illegal, but they're what security teams actually focus on.

Money laundering: Using casino accounts to move funds. This is a compliance issue more than a gaming one.

Card counting doesn't even make the list for online play. The architecture makes it irrelevant.

The Honest Math

Let me be direct about expected value:

The "countable" column for physical casinos shows a range because your EV depends on the count. With good penetration and proper bet sizing, skilled counters can achieve a 0.5-1.5% edge. With poor penetration, even a perfect counter might have negative EV after factoring in the time spent at low counts.

Live dealer online falls somewhere in between—technically countable, but the practical edge after accounting for limited penetration and bet restrictions is likely negative or barely positive.

Why I Built the Calculator Anyway

So why build a tool for a technique that doesn't work online?

Three reasons:

1. Physical casinos still exist. Las Vegas, Macau, local card rooms—these are environments where counting works. If you're going to play there, understanding the math transforms gambling into something closer to informed investing.

2. Understanding the math is valuable on its own. Knowing why you have an edge (or don't) is the difference between gambling and advantage play. Even if you never count cards, understanding probability, expected value, and variance makes you a better decision-maker.

3. Training before real play. You can't practice counting at a live table without risking money. Using a calculator to internalize true count adjustments and optimal strategy deviations means you arrive at the casino prepared.

The Bottom Line

If someone is selling you a system to beat online blackjack through card counting, they're either confused or lying. The games are designed—mathematically, architecturally—to be immune.

Save your advantage play for environments where the math actually works: physical casinos with good penetration, reasonable bet spreads, and shoes that don't shuffle every hand.

And if you're playing online? Treat it as entertainment with a known cost. Set a budget, play basic strategy, and don't fool yourself into thinking you have an edge you don't have.

The house always has a way of protecting itself. Understanding how they do it is the first step to finding the situations where you can actually turn the tables.

Want to learn basic strategy perfectly before hitting a real casino? Try the calculator and see how optimal decisions change as the deck composition shifts.