https://massive.com/blog/insider-and-institutional-ownership-data-via-massives-apis-forms-3-4-and-13f
Insider and Institutional Ownership data via Massive’s APIs (forms 3, 4, and 13F) | Massive
Apr 30, 2026 - Massive now exposes three insider and institutional disclosure datasets in our REST API: form 3, form 4, and form 13F.
institutional ownership data