Insider buying refers to open-market purchases (SEC transaction code P) made by corporate officers, directors, or beneficial owners of more than 10% of a company’s shares. These voluntary purchases are distinct from stock grants, option exercises, or other non-market transactions.

A cluster buy occurs when multiple corporate insiders purchase shares of the same company within a short time window (typically 30 days). Cluster buys are considered a stronger bullish signal than a single insider’s purchase, because they suggest broad internal confidence in the company’s prospects.

Under SEC rules, insiders must file a Form 4 within two business days of a transaction. Average Insider processes these filings shortly after they appear on EDGAR, so recent purchases are typically visible within hours of the filing.