What is line movement in sports betting?

Every market has an opening line, a series of current lines and a closing line, which is the last number posted before the game starts. Movement shows up in two places. The number can change, as when a spread goes from -3 to -3.5, or the price can change while the number stays put, as when a total sits at the same figure but one side gets more expensive. Both count as line movement, and both change what a wager costs.

Lines move for several reasons that can overlap: news such as an injury, a lineup or the weather; wagers from accounts the operator respects; heavy volume on one side that an operator wants to rebalance; and other operators changing their own numbers, which the rest tend to follow. Because each cause can produce the same-looking move, the reason behind a given move is an inference. Timing helps, since a sudden jump right after an injury report points toward news, while a slow drift over several days is harder to explain.

When you read a move, record three things: which operators moved, how quickly, and whether the number or only the price changed. A move that appears at one operator and nowhere else may be that operator managing its own exposure rather than the market learning something new. Compare the move with the news timeline and with what other operators did before you draw any conclusion.