In the United States several strands are public. Members of Congress must disclose securities transactions within forty-five days, large managers file quarterly 13F holdings reports, and company officers and directors file Form 4 within two business days of trading their own shares.
All of it arrives late, and the lag varies. Form 4 insider trades are nearly current; 13F holdings can be six weeks stale by publication, by which time the portfolio may have been rebuilt entirely.
Read it as context, never as an entry signal. Its value lies in spotting persistent accumulation across a sector, or a cluster of insiders buying their own stock with their own money, which historically carries more information than any single large trade.