About 13f-changes

13f-changes tracks quarter-over-quarter changes in selected hedge funds' Form 13F-HR filings with the SEC. Unlike most 13F tools, the site is organized around what shifted rather than the static list of holdings.

What's a 13F?

Form 13F-HR is a quarterly disclosure filed by institutional investment managers with at least $100 million in qualifying U.S. equity securities under management. It lists every long equity position held at quarter-end. Filings are due 45 days after the quarter ends.

What 13Fs cover

• Long equity positions in U.S.-listed common stock, ADRs, and certain ETFs.
• Listed call and put options (reported separately from the underlying).
• Convertible debt, certain warrants.

What 13Fs don't cover

• Short positions.
• Bonds and most fixed-income holdings.
• Foreign-listed shares not on U.S. exchanges.
• Derivatives positions held outside the reporting entity.
• Currency, commodity, or futures positions.
• Anything held in non-13F-reporting vehicles.

Data sources

• Filings: SEC EDGAR (www.sec.gov) — the primary source.
• CUSIP → ticker: OpenFIGI free API.
• Sector / industry: Yahoo Finance via the yahoo-finance2 library, mapped to canonical GICS top-level sectors.
• Themes: assigned editorially per-fund during a quarterly review session. Themes are an opinionated layer on top of the canonical sector data — Amazon's primary GICS classification stays "Consumer Discretionary," but it can also be tagged "AI infrastructure" if that frames the fund's thesis better.

Refresh cadence

A GitHub Action polls EDGAR daily during the four 45-day filing windows (mid-Feb, mid-May, mid-Aug, mid-Nov). When a new filing lands, a manual review session ingests it, classifies any new positions, computes the diff, and ships.

Limitations

• Filing-snapshot values. Position values are as of the filing's quarter-end date — not refreshed with current market prices.
• Options vs. underlying. Listed options on the same security are shown as separate rows, with a "Call" or "Put" annotation.
• Foreign-listed shares. Some foreign-listed CUSIPs (G-prefix) are present; resolution to local tickers is best-effort.
• Theme tags are editorial. Different observers would categorize positions differently; tags are one perspective.