One difference between these two games causes every other difference: Klondike deals most of its cards face down, and FreeCell deals all of them face up.
That is why about 18% of Klondike deals cannot be won by anyone, while in FreeCell the figure is roughly one deal in ninety thousand. It is why losing at Klondike is often bad luck and losing at FreeCell is almost always a mistake. And it is why the two games feel completely different to play even though they look like cousins on screen.
Side by side
| Klondike | FreeCell | |
|---|---|---|
| Cards face down at the deal | 45 of 52 — 21 in the columns, 24 in the stock | none |
| Deals winnable with every card known | 81.9% at Turn 3, 90.5% at Turn 1 | 99.9989% |
| Deals this site's hint wins by itself | 12.4% at Turn 3, 45.6% at Turn 1 | 97.2% |
| What limits you | the stock, and what it gives you | four free cells |
| Where the difficulty comes from | information you do not have | planning far enough ahead |
| A loss usually means | the deal, or a guess that failed | a line you did not see |
The winnable figures come from the Solvitaire project at the University of St Andrews, playing the "thoughtful" version of each game, where every card is known. The hint figures we measured on this site's games, letting the hint play each deal on its own.
That caveat matters very differently for the two games. For Klondike, thoughtful play is a much easier game than the one you sit down to, so 81.9% is a ceiling you will never approach. For FreeCell, thoughtful play is essentially the game as dealt — so 99.9989% is close to the truth of what is in front of you.
What each game asks of you
Klondike asks you to manage uncertainty. You cannot know whether the card you need is reachable, so good play is about keeping options open: uncovering face-down cards early, not sending low cards home before the columns are done with them, not emptying a column without a king to put in it. You are playing the odds of a deck you cannot see.
FreeCell asks you to see further. Nothing is hidden, so there is no luck to manage — there is only whether you worked out the consequences of a move before you made it. A FreeCell deal is a puzzle with an answer in it, and your job is to find the answer rather than to survive the shuffle.
The stock versus the free cells
Klondike's stock is a resource that arrives on a schedule you do not control. At Turn 3 only every third card comes up on top, so part of the deck can stay out of reach for the whole game. You spend passes through it, and the scoring charges you for them.
FreeCell's four cells are a resource you control completely and can ruin instantly. The research is stark on this: with four cells almost every deal is winnable, with two it drops to about 80%, and with one to 19%. Every card you park in a cell takes a slice of that away until you take it back out. Running the cells down to one open slot for a clever move is the most common way a winnable FreeCell deal is lost.
Which should you play?
Play Klondike when you want something to do with your hands — a game you can start without committing to think hard, where some deals go well and some were never going to, and the next one is a click away. The randomness is a feature when you are not in the mood to concentrate.
Play FreeCell when you want a problem. There is nothing to blame, every deal has an answer, and a loss is information about how you played. It is the better game for actually getting better at something.
A practical note: FreeCell rewards undo far more than Klondike does. In Klondike, stepping back is a gamble on cards you still cannot see. In FreeCell, every card was visible the whole time, so the mistake is findable and undo is the tool for finding it.
If you only play one
Start with Klondike if you want the game you already know, and switch to FreeCell the first time a Klondike deal collapses through no fault of yours and you want something that would not have done that.
More on the odds behind both: is every game of solitaire winnable and is every FreeCell game winnable.