When people track insider buying stocks, they are chasing one of the most studied signals in markets: executives putting their own cash in. Academic research has long found that insider purchases tend to outperform, which is why the insider buying vs selling ratio gets watched more closely than any single trade.
One director buying is a data point. Five insiders buying while nobody sells is a statement. Trackers that split buys from sells keep you from mistaking option exercises and tax sales for conviction. The ratio is the context that makes a single buy meaningful instead of just interesting.
Focus on open-market buys, the ones where an insider spends real money at market price. Those are the purchases the research keeps flagging. Grants, gifts, and option exercises ride along in the same filings and mean nothing at all.
One more filter worth adding: compare the buy to the insider's existing stake. A director doubling a small position is conviction. A billionaire adding 0.1% is a headline, not a signal. Size your attention to the percentage, not the dollars.
Ignore the noise. Follow the money that chose to be there.