One Lie is a free daily deduction puzzle, playable in any browser with no account. It launched on 18 September 2026 and publishes one new case every day at midnight New York time.
Every One Lie case has exactly one solution, and that solution is reachable by logic alone. This is not an aspiration — it is checked. Each case is audited by brute force against all 1,296 possible codes to confirm that exactly one code has exactly one false statement among its clues. A case that fails the audit is never published.
The practical consequence: a careful solver can crack any case on the first attempt without guessing. The attempts exist to forgive arithmetic slips, not to make room for luck — which is why the harder modes allow fewer of them.
The puzzle for a given day is a pure function of the date. There is no server deciding what today’s case is, which means everyone in the world sees the same statements at the same moment, and the game keeps working if the backend does not. The day rolls over at midnight in New York, handled with proper daylight-saving arithmetic rather than a fixed UTC offset.
| Mode | Code length | Statements | Attempts |
|---|---|---|---|
| Easy | 3 digits | 4 | 3 |
| Medium | 4 digits | 5 | 2 |
| Hard | 4 digits | 6 | 2 |
Difficulty comes from the kind of statements involved, not from how much searching is required. Easy and Medium lean on direct statements about single positions; Hard leans on arithmetic across the whole code.
There is no account, no login and no tracking pixel. Your streak, statistics and scratchpad are stored in your browser. The leaderboard stores a random device identifier, the day, your result and an optional display name. IP addresses are never stored in readable form.
There is a contact form on the game page — open One Lie and choose Contact in the footer. Messages go straight to the person who built it. Leaving an email address is optional and is only ever used to reply.
One Lie has been running daily since 18 September 2026. It is finished and free to play; there is nothing to sign up for and nothing to buy. If something is broken, or a puzzle felt wrong, the contact form on the game page reaches the person who built it.