How does a libero replacement work in volleyball?

The libero can enter and exit the court freely before any rally, replacing any back-row player, without it counting as a substitution. The exchange happens in the replacement zone during a dead ball.

Full Explanation

Per FIVB Rule 19.3.2, a libero replacement is an exchange between the libero and one of the back-row players. It is not considered a substitution and there is no limit on replacements per set. The replacement may take place before any rally, provided the player to be replaced has completed at least one rally on the court. The exchange must occur in the libero replacement zone (between the attack line and the end line, on the sideline near the scorer's table) during a dead ball. The same player who left the court must return when the libero exits; the libero cannot be replaced by a different player.

Rulesets covered: FIVB  |  Rule Reference: FIVB Rule 19.3.2