What “winnable” means here
A deal is winnable if there is at least one sequence of legal moves that clears the board. Some random shuffles have no such sequence: however well you play, you will lose. A site that deals purely random shuffles will therefore sometimes hand you a game that was lost before you started.
The games on this site avoid that by dealing only from libraries of deals that were checked ahead of time. You can play them in the games above, or go straight to Solitaire, Spider or FreeCell.
How a deal gets into the library
- Shuffle. A random deck is generated for the game variant.
- Search. A solver program searches for a full winning sequence of moves. It runs under a time and memory budget, so it gives up on deals that are hard to solve.
- Replay. If the solver finds a win, the entire move list is replayed from the starting layout through the same rules code that runs in your browser. If any move is illegal, or the final position is not a win, the deal is thrown away.
- Keep. Only deals that pass the replay go into the library.
When you start a game, the site picks a deal from the library and relabels its suits in a way that keeps it exactly as winnable (for Klondike and FreeCell the two red suits and the two black suits are swapped; for Spider any suit mapping works). This gives many different-looking games from each verified deal.
What was measured
| Game | Verified deals in the library | Random deals tried | Won by the solver within budget |
|---|---|---|---|
| Solitaire, Draw 1 | 186 | 100 | 49 (49%) |
| Solitaire, Draw 3 | 60 | 60 | 29 (48%) |
| Spider, 1 suit | 60 | 60 | 60 (100%) |
| Spider, 2 suits | 17 | 30 | 21 (70%) |
| Spider, 4 suits | 24 | 70 | 14 (20%) |
| FreeCell | 80 | 60 | 60 (100%) |
The last column is not the share of random deals that can be won. It is only how often our solver found a win within its time budget; some of the deals it gave up on were probably winnable too. It is a lower bound.
What this does and does not promise
- It promises that a winning line exists for every deal in the library, and that the line was checked against the game's own rules.
- It does not promise that the win is easy, or that you will find it. Spider with 4 suits in particular can be very hard even when a win exists.
- It does not promise that the deals are a perfectly representative sample of all random deals. A solver tends to find wins in easier deals more often than in very hard ones, so the library leans a little easier than a pure shuffle would be.
- If the list of verified deals cannot be loaded (for example, if your connection drops), the game falls back to a random shuffle and says so in the badge above the table. You can also turn verified deals off in Settings if you prefer a pure random shuffle.
How common are unwinnable deals?
It depends on the game. In FreeCell almost none: of the first 32,000 numbered Microsoft deals, only deal 11,982 has no solution. In Spider with one suit it is also rare. In Klondike, published solver research puts the share of winnable deals at roughly 80 to 90 per cent depending on the rules and on whether the player can see the face-down cards, which leaves a real minority that cannot be won. In Spider with four suits, wins are far harder for people to find than for a computer with unlimited time, so many random games feel lost even when they are not.
Frequently asked questions
What does winnable mean?
A deal is winnable if some sequence of legal moves clears the board. Some random shuffles have no such sequence.
How do you check that a deal is winnable?
A solver searches for a complete winning line, and the whole line is replayed from the starting layout through the same rules code that runs the game. Only deals that pass the replay are kept.
Does a winnable deal mean it is easy?
No. It means a win exists. Finding it can still take careful play, especially in Draw 3 Solitaire and in 4-suit Spider.
What happens if the verified deals cannot be loaded?
The game falls back to a random shuffle, which may be unwinnable, and the badge above the table changes to say so.