Random Number Generators (RNGs) are essential for ensuring fairness and unpredictability in online Blackjack. They simulate the random shuffling of cards, determining the outcome of each hand by randomly selecting cards for both the player and the dealer. This guarantees that no hand is predictable and that each card dealt is independent of previous ones. RNGs are rigorously tested to prevent bias, ensuring the game remains fair. While they don't change the house edge, they ensure that the randomness needed for the game to function correctly is preserved, making it impossible to predict the outcome of any given hand.