Brain Games20 Questions game
The classic guessing game, with an AI on the other side. You can ask the questions, or let the AI ask you.
The AI thinks of something. You find out what it is with 20 yes-or-no questions.
Your questions and answers in this game are sent to an AI model (DeepSeek, or OpenAI as a backup) to get a reply. Don't type anything personal.
How to play
- Choose who guesses. "You guess" means the AI thinks of something. "AI guesses" means you do.
- You guess: type a yes-or-no question, like "Is it an animal?". The AI answers Yes, No, Sometimes or Not sure.
- When you think you know, ask "Is it a giraffe?". Name it right and you win.
- AI guesses: think of something and keep it to yourself. Answer each question with the buttons.
- Either way, you get 20 questions. If you're stuck, press "Give up" to see the answer.
How 20 Questions works
One player thinks of something. The other asks up to 20 questions that can be answered yes or no. The goal is to name the thing before the questions run out.
It's a very old parlor game. It was a radio quiz show in the US in the 1940s, and handheld 20Q toys did the same trick with a built-in computer in the 2000s.
Why 20 questions is enough
Each yes-or-no answer can cut the possible answers in half. Twenty halvings split about a million things (2²⁰ is 1,048,576). So a good player with good questions can, in theory, find almost anything.
That's why broad questions come first. "Is it alive?" splits the world in two. "Is it a red apple?" only rules out one thing.
Tips for the guesser
Start with big groups: alive or not, natural or man-made, bigger or smaller than a shoe, found indoors or outdoors.
Keep track of what you know. If it's an animal that lives in water and isn't a fish, think whales, dolphins, seals.
Don't guess too early. A wrong guess uses a question just like any other.
About the AI
The answers come from an AI language model. We use DeepSeek first and an OpenAI model as a backup if DeepSeek is down. In our own tests it answered tricky yes-or-no questions correctly 19 times out of 20.
So it's good, not perfect. If an answer looks wrong, ask again in different words. Things like size or color can be fuzzy, which is what the Sometimes answer is for.
Your messages are only used to get the reply. We don't save them. Please don't type names, addresses or anything private.
FAQ
- Can I play 20 Questions online for free?
- Yes. There's no sign-up and no download. Pick "You guess" or "AI guesses" and press Start.
- What can the AI think of?
- Everyday things: animals, food, objects around the house, nature and famous places. It picks at random, so every game is different.
- What can I think of when the AI guesses?
- Almost anything: an animal, an object, a food, a place or a famous character. Very obscure things are hard for it, just like for a person.
- Is the AI always right?
- No. It's right most of the time, but it can slip on fuzzy questions. If something looks off, ask the same thing a different way.
- Why do I sometimes see "slow down"?
- There's a limit on how many questions one visitor can send per minute. It stops bots from overloading the game. Wait a minute and carry on.
More brain games
- Schulte tableTap the numbers from 1 upward as fast as you can. The clock starts when you press Start and stops on the last number.
- Stroop testA color word shows up in a different color of ink. Press the ink color as fast as you can. Your brain wants to read the word, and that's the whole test.
- Tower of HanoiMove the whole stack to the right peg. Only one disc at a time, and never a bigger disc on top of a smaller one.
Last updated 2026-11-06