Sportsbook Line Moves — Sharp Action, Steam, and Reverse Line Moves Explained
A 'line' is a sportsbook's odds for a given bet — point spreads, totals, moneylines. When the line moves (e.g., Chiefs go from -10 to -7.5), money has come in on one side strongly enough that the book adjusted to balance its risk. Reading why the line moved (which side the money came from, whether sharp or square, how quickly) is one of the highest-leverage skills in sports betting.
What's 'sharp money' vs 'public money'?
Public (square) money: the casual bettor crowd, which leans toward favorites, big names, and overs. Sharp money: known professional bettors and syndicates — much smaller in number but with disciplined, model-based approaches. Books track wager sizes and history; a $50K bet from a known sharp moves the line, while $500K of $25-ticket public bets often doesn't.
What's a 'steam' move?
A steam move is a fast, simultaneous line shift across most or all books — usually triggered by a sharp syndicate placing big bets at multiple shops at once. Steam typically signals that a respected sharp model has an edge. Some sharp bettors live to chase steam (a 'steam chaser'), trying to hit a softer book before it can adjust.
What's a reverse line move (RLM)?
A reverse line move: 80%+ of the public bets one side, but the line moves the OTHER way. That tells you the small handful of sharp bets on the under-bet side were larger than all the public action combined. Books happily fade the public, so RLMs are one of the cleanest sharp signals available.
Where do I track line moves?
Free: VSiN, Vegas Insider, Action Network's free tier. Paid: Action Network Pro, Don Best (institutional), Pickswise. Most pro bettors run an alert system that pings when a line moves more than X points or when steam hits across N books.