Everything people commonly ask about Deduce, the free daily logic-grid detective puzzle. If your question is not here, the guide to solving logic-grid puzzles covers method and the verification page covers how cases are built.
Deduce is a free daily logic-grid detective puzzle. Each case gives you a victim, a set of suspects, a set of rooms and a set of weapons, plus a list of clues. Exactly one combination fits every clue, and your job is to find it and file a single accusation: who did it, where, and with what.
Yes. Every daily case and the whole archive of past cases are free, with no paywall, no advertising and nothing to buy. There is no app to install — it runs in a browser on a phone, tablet or computer.
Yes. You can play the daily case anonymously and your solve still appears on the leaderboard under an anonymous handle. An account is free and keeps your solve streak, your progress between devices, and unlocks the higher detective ranks.
They belong to the same family of puzzle: a murder mystery solved on a logic deduction grid, with a new one every day, free in the browser. If you enjoy Murdle you will recognise how a Deduce case works immediately.
Three differences. Deduce cases are generated and machine-verified by a constraint solver rather than hand-written, so every published case is proven to be solvable by deduction alone. Difficulty is a progressive ladder of five detective ranks you unlock by solving, rather than a weekly cycle. And the top rank adds a fourth axis — the time each suspect arrived — on a five-by-five board.
Read the clues, then use the grid to rule out what cannot be true. Negative clues ("not in the library") are usually the most useful, because each one removes a possibility permanently. When a row has one square left uncrossed, that square is true. When the board is complete, file your accusation. A wrongful arrest ends your streak, so it pays to finish the grid rather than guess.
Yes. A new case opens at midnight UTC and closes at the next, and it is the same case for every detective that day — so times on the leaderboard are directly comparable.
Yes. Every case that has closed stays permanently playable in the case archive, which currently holds several hundred cases. Solutions are never published there.
Five, in order: Rookie Detective, Junior Investigator, Inspector, Master Detective and Grand Sleuth. Junior is where you start and Rookie is a lighter practice tier; Inspector unlocks at 10 solves, Master Detective at 20 and Grand Sleuth at 40. Each rank adds new kinds of clue rather than simply adding more of them.
It depends on the rank. A Rookie case is six to eight clues, all of them direct statements of fact. An Inspector case allows chains up to three inferences deep, and adds witness statements. A Master Detective case runs up to thirteen clues with chains five deep, and introduces motives and clues that contradict each other, so one of your witnesses is lying. A Grand Sleuth case runs to twenty clues on a five-by-five board with a fifth axis. Most detectives take ten to twenty minutes.
Yes, and the guarantee is stronger than that. A constraint solver checks two separate things before a case is published: that only one suspect, room and weapon combination fits the clues, and that the entire grid collapses to exactly one consistent arrangement. A case that satisfies the first but not the second is discarded, because it would leave a player able to name the killer without being able to prove the rest.
Every published case is. The generator proposes a case, a solver works it the way a player would — clue by clue, recording what each one eliminates — and the case is rejected unless it passes every check. Cases that fail are thrown away rather than softened. You can read the full process on the puzzle verification page.
No, and this is checked rather than assumed. The verification step confirms the solution is reachable by deduction from the clues given, so if you find yourself guessing you have missed something rather than run out of information.
At deduce.studio, in any modern browser. There is no app store download and no installation.