The riffle force is a classic card forcing technique in which a magician appears to offer a free choice by flipping — or “riffling” — through a deck of cards, and inviting a spectator to glimpse any one of the cards, at any point. Secretly, the magician ensures the spectator sees only one or a few predetermined cards. The riffle force is usually achieved by maintaining a subtle break at its location.

The riffle force relies on natural hand movements and timing: as the magician riffles the deck and the spectator says “stop,” the deck is split precisely at the break, so the riffling is paused for 100 or 200 ms and at that moment only one playing card is discernible.

The method is valued for its fairness and deceptiveness, as the spectator perceives complete freedom in their selection. Riffle force is quick to learn, practical in performance, and highly effective when executed smoothly, making it a staple among magicians for both beginner and advanced routines. Variations exist, including using the top or bottom card, and employing different grips or subtleties to enhance the illusion of choice. The riffle force remains one of the most convincing and widely used card forces in magic.