A shuffle is when all the candies on the board are shuffled. The colours of the candies do not change, but their position on the board does. A shuffle can be brought on when a player runs out of possible switches on the board. It was possible to use the shuffle booster to get the same effect, however it is not available for now.
When a player runs out of possible moves, all the candies go into a pink bag in the centre of the screen and are then shook and then they come out of the bag shuffled randomly. All regular candies and Candy Bombs are shuffled. At the top of the screen during a shuffle it will read, "No more possible switches! Shuffling.". (Note: The bag does not appear on mobile versions, it just simply read that there are no possible switches.)
In the case of coconut wheel and colour bomb, they have to be stuck among blockers or ingredients, since a free coconut wheel or colour bomb can always make a move.
Shuffling does not cost anything, but on Web prior to the release of Sour Salon, it used to cost 5 seconds for timed levels or one move for other types of levels. If a shuffle occurs with only 1 move left, the player would lose a life without seeing the shuffle animation and the reason for failure will be: "No more possible switches". Similarly, in timed levels, the player would automatically fail the level if there are no more viable switches when the time remaining is less than 5 seconds.
This behaviour was also corrected on mobile, at v1.72 or earlier. Before that version, shuffle would take 2 seconds off the clock.
After a shuffle, there would be a possible move, unless there are not enough candies to form a single move, in which case player will immediately fail the level without any option to continue by spending gold. This is one of the few methods of rendering an attempt unwinnable.
Sometimes a shuffle can be very useful, for example, when there are no possible switches where all the jelly is, then after shuffling the jelly can be reached.
It also applies to levels with fixed candy layouts, which does not have a match in the beginning but something else may ruin the setup. Examples include levels 1221 and 1253.
The bag that is used for shuffling in web version has the logo of Candy Crush Saga on it.
It is possible for a double shuffle to occur, but this is very rare indeed. What has to happen is that the first shuffle happens and after the shuffle, the only possible move is then blocked by a chocolate, bringing on a second shuffle. Double shuffles can also happen with chameleon candies, where in the second shuffle happens after the chameleon candies change colours following the first shuffle. In that case, there are still no possible moves after the first shuffle because the Chameleon Candies have changed their colours. What can also happen is that the shuffle causes a combination to occur, upon which no other combinations can be made, and the shuffle happens again without any moves being used.
This does not happen on mobile version since shuffle only occurs after every other object (chocolate, tornado, rainbow candy, conveyor belt) has taken action.
The only case of double shuffle on mobile is that a shuffle causes a match, and after that, there are no more moves again, causing another shuffle.
Although rare, shuffling may also occur immediately after the level starts, most notably in levels such as 303 and 472.
On web version, candies are put into different places after a shuffle, sometimes matching 3 of the same kind. This can make you furious. For example, if it match with 3 of the same kind including the wrapped candy, it may blow up a striped candy nearby. The striped candy may be reserved because you want to match it with the wrapped candy and vice versa. However, shuffling may rarely give you colour bombs, which may be useful.
Before the candies are shuffled, they briefly appear as if they had already been shuffled, hence allowing the player to make a rough prediction as to the shuffle's usefulness.
On mobile, it was extremely unlikely to gain a match as the candies were always put in a fashion where another match is needed. However, it gets more common in recent updates.
On web version after Candy Keep was released, striped candies and wrapped candies will stay in place. However, candy bombs will be shuffled. It made many levels like 445 and 734 easier as the bombs will be easier to defuse or the special candy will stay in place. It was vice versa in the past.
Later, this phenomenon was also applied to mobile.
In mobile, its Oh No! screen is one of the game over screens that has an End Game option after the change on its interface. The other one is if the player presses the quit button after making a move in non-timed levels and Timed levels and destroying the Magic Mixer when the blocker order that created from them are not all collected.