Is every game of Klondike Solitaire winnable?

No. Around 82% of Klondike deals are solvable with perfect play and full knowledge of the face-down cards. Playing normally, without that knowledge, typical win rates are about 33% for Turn 1 and about 11% for Turn 3. This site solves each deal in the background and tells you which kind you got.

What is the difference between Turn 1 and Turn 3?

Turn 1 flips one card from the stock at a time, so every card in the deck is reachable. Turn 3 flips three and only the top one is playable, putting two thirds of the stock temporarily out of reach. The difference is large: typical win rates are about 33% for Turn 1 against about 11% for Turn 3.

Can I move cards off a foundation?

Yes. Moving a card back from a foundation into the tableau is legal in Klondike and is occasionally the only way to unblock a column. It is rare that it helps, but the option is there.

What can go in an empty column?

Only a King, or a correctly-stacked run starting with a King. This is a rule people often forget, and it is why clearing a column with no King available can leave you worse off than before.

How long does a game take?

About 10 minutes for a typical Klondike game.

How to Play Klondike Solitaire — Rules Explained

How to Play Klondike SolitaireLearn Klondike Solitaire in five minutes: the layout, the two building rules, how the stock works, and how to win. Plain language, no jargon.