About Veintiuno
Veintiuno (Spanish for “twenty-one”) is an app for learning to play blackjack properly, made in Spain by independent developer Iván Sevilla.
Why it exists
Much of what’s written about blackjack online comes from sites paid to send you to a casino. That’s why “tricks to win” are everywhere and honest explanations are rare. Veintiuno does the opposite: it teaches the correct decision and explains why, with no real money and nothing to sell except the app itself.
Where the charts come from
Basic strategy isn’t an opinion: it’s the play with the best expected value for each combination of hand, dealer card and rules. Our charts start from the standard six-deck chart and apply the changes each rule introduces (decks, soft 17, hole card, double after split, doubling restrictions and surrender).
They’re checked against the standard references: the original 1956 work by Baldwin, Cantey, Maisel and McDermott, Edward Thorp’s Beat the Dealer, Peter Griffin’s analysis, and the charts and calculators published by Wizard of Odds and BlackjackInfo. House-edge figures are approximations based on Wizard of Odds’ rule-effect tables.
The chart on this site runs on exactly the same engine as the app, so they always agree.
What we don’t do
- No affiliate links to casinos or sportsbooks, no bonuses, no operator reviews.
- No promises that you’ll win money. Blackjack has a house edge, and we say so.
- The app has no real-money play.
Contact
Spotted a mistake in a chart or explanation? Email ivan.sevilla.ruano@gmail.com. We’ll check it and, if you’re right, fix it on the site and in the app.