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Decision trainer
Instant feedback on every hand
Train hard totals, soft totals, pairs, doubles, and surrenders against the chart for your rules. Wrong plays come with the reason, not just a red X.
iPhone · Free to start
Make the right move. Every hand.
Blackjack trainer for basic strategy, table-rule variants, and Hi-Lo counting.
Basic strategy
Hi-Lo counting
Made for iPhone
Hi-Lo countingFlash, running count, ramp
Instant feedbackLearn every decision
A better way to learn
Practice built around real decisions.
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Curriculum
40+ lessons, in order
Fundamentals through pairs, advanced edge, and Hi-Lo. Quizzes and chart highlights so the math sticks beside the muscle memory.
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Card counting
Flash, running count, ramp
Build speed with Hi-Lo recognition, hold a running count through timed sequences, then let Ramp Mode push the pace.
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Reference
A chart that matches your table
Color-coded basic strategy for H17/S17, DAS, and surrender. Tap any cell for the recommended play and why it wins more often.
The TwentyOne journal
Strategy, explained without the noise.
Table rules
Blackjack Insurance Explained: Is It Ever Worth It?
Blackjack insurance pays 2:1 if the dealer has a ten-value card under an Ace. For a basic-strategy player, the math says decline it—including even money.
Card counting
Running Count vs True Count in Blackjack: Explained
The running count tracks Hi-Lo tags as cards are exposed. The true count adjusts that number for decks remaining, making the same count comparable at different points in the shoe.
Basic strategy
When to Surrender in Blackjack: The Basic Strategy Guide
Surrender looks like giving up, but in the right blackjack hands it saves money. Learn exactly when basic strategy says to surrender—and when it doesn’t.
Table rules
3:2 vs 6:5 Blackjack: Why the Payout Matters
A 3:2 blackjack pays $15 on a $10 bet; 6:5 pays only $12. That small-looking difference adds roughly 1.4 percentage points to the house edge, all else equal.
Basic strategy
When to double down in blackjack
Doubling is one bet, one card, and the highest-EV press in basic strategy. Here is when to double hard totals and soft hands — and when the table rules move the cell.
Card counting
Hi-Lo card counting explained
Hi-Lo assigns +1, 0, or −1 to each rank, then keeps a running count. It is a memory drill with a purpose — not a promise that the shoe is yours.
Questions
Before you download.
Straight answers about the trainer, basic strategy, and what is included.
Is TwentyOne real-money blackjack?
No. TwentyOne is an educational trainer only. There is no wagering, no chips with cash value, and no connection to any casino or sportsbook.
What is basic strategy?
Basic strategy is the mathematically best play for every starting hand against every dealer upcard. It tells you when to hit, stand, double, split, or surrender so the house edge stays as low as the rules allow.
Does basic strategy guarantee a win?
No. Correct basic strategy reduces the house edge; it does not remove it. Short-term results still swing with variance, which is why the app focuses on decision quality, not session outcomes.
Can I match the rules at my casino?
Yes. Set H17 or S17, double after split, and late surrender so the strategy chart and decision drills match the plaque on the table you actually sit at.
What is Hi-Lo card counting?
Hi-Lo assigns a value to each card (+1, 0, or −1) so you can track whether the remaining shoe favors the player. TwentyOne teaches recognition, running count, and speed drills — not a shortcut to guaranteed profit.
What is free vs. premium?
Module 1 — fundamentals and your first drills — is free. Premium unlocks the full curriculum, unlimited decision practice, Hi-Lo counting modes, and detailed session stats. Monthly, annual, and lifetime plans are listed on the App Store.
Can I practice offline?
Yes. Lessons, the strategy chart, and practice sessions work without a connection. Progress stays on your device until you choose to back up through iCloud.
Which devices are supported?
TwentyOne is built for iPhone. It runs on any device that meets the current App Store requirements for iOS. There is no Android or web version today.
TwentyOne on iPhone
Drill the play until it is automatic.
Instant feedback on every decision, a full basic-strategy chart for your rules, and Hi-Lo drills when you are ready to count.
