13F API: pulling SEC fund holdings as structured data

A 13F API serves the holdings inside SEC Form 13F-HR filings as structured data you can query, instead of leaving you to parse EDGAR yourself. Institutional managers with at least $100 million in 13(f)-eligible US securities file quarterly, listing long positions by CUSIP with share counts and market values. The filings are public and free. What an API is actually selling is the work between the raw filing and a row you can join to your own data: identity resolution, change computation, and a filing date attached to every value.

What the raw filing gives you, and what it does not

A 13F-HR information table is a list of rows: issuer name as typed by the filer, class title, CUSIP, value, shares or principal amount, investment discretion, and voting authority. That is the whole of it. Everything a research desk actually wants has to be built on top:

• A stable security identity. CUSIPs are reliable identifiers, issuer names are not. The same company appears under several spellings across filers and across quarters.
• A stable filer identity. Managers file under a CIK, but names change, and families of related filers need mapping if you want one view of a group.
• Change between quarters. New, added, trimmed and exited positions are computed by differencing consecutive quarters. No filing states them.
• Amendments. A 13F-HR/A restates a prior filing. Data that silently keeps the original is wrong, and data that silently replaces it without keeping the amendment date is unauditable.
• Notice filings. A 13F-NT reports that holdings are being reported by another manager. It has no holdings table, and treating it as an empty portfolio is a common error. See 13F-HR vs 13F-NT.

What to require from a 13F API

Since the underlying filings are the same for everyone, the differences between providers are handling differences. Worth checking before you build on one:

• A filing date on every row, so staleness is visible in your own systems rather than assumed.
• A source link per holding, so any figure can be verified against EDGAR without a support ticket.
• Explicit amendment handling, with the amendment and the original both retrievable.
• Deterministic pagination and stable ids, so an incremental sync does not skip or duplicate rows.
• Coverage you can enumerate. Which filers, from which quarter, is a question with a factual answer. Vague coverage claims are a reason to test before committing.
• Push, not just pull, if your workflow is event-driven. Polling a quarterly dataset every hour wastes both sides' capacity.
• No advisory framing. A data API returns disclosures. Scores that imply a recommendation put your compliance function in the loop for no benefit.

Cross-filer questions are the interesting ones

One fund's 13F is a single portfolio. The queries that justify an API are usually cross-filer: who else disclosed this security this quarter, which filers moved in the same direction, where do independent managers hold the same names. That is a join across every filer for a quarter, which is exactly the sort of thing that is painful to do from raw EDGAR files and cheap to do against a normalised store. Flock records these overlaps as convergence events.

If you are also covering registered funds, note that 13F is not the only US holdings disclosure: N-PORT vs 13F covers the differences in scope and frequency, and 13F vs 13D covers the difference between a quarterly holdings report and a 5 percent beneficial-ownership filing.

What Flock's API exposes

Flock's Business plan is a REST API over normalised India and US disclosure data, at ₹39,999 per month, with annual billing at ₹3,49,999 and an included allowance of 100,000 requests per month. The current v1 surface is:

Authentication is a bearer API key, scoped per endpoint group, with sk_test_ and sk_live_ prefixes and an OpenAPI spec published for the surface. The published SLA is 99.5 percent. Access starts with a conversation rather than a self-serve signup: the details, including the fact that invoices currently carry no GSTIN because Flock is not GST-registered, are on the business page.

The honest limitation

No 13F API can make 13F data current, because 13F data is not current. Two lags stack: the filing reports holdings as of quarter-end, and the manager has up to 45 days after that to file. Any product built on it inherits that, and the useful thing an API can do is make the staleness explicit on every row rather than hide it. For the filing itself, see what is a 13F filing, and for the browsing equivalent of this data, 13F tracker.

Flock reads primary filings and stamps every data point with its source and date. What the data means for you is your call to make. This is not investment advice.