← FORM4API

// about

About Form4API

Built and operated independently from Sweden · Last updated June 2026.

What this is

Form4API is a developer-first REST API for U.S. SEC filings that move markets when insiders touch them: Form 4 insider transactions, Form 144 intent-to-sell disclosures, and 13F-HR institutional holdings. Real-time ingestion from EDGAR, amendment-aware parsing, post-trade returns, cluster-signal detection, and webhooks. See the insider trading API overview or the full reference.

Who built this

I'm Theodor Nielsen, founder of Form4API. I built and operate the service independently from Sweden.

Form4API exists because the data feeds that retail quants, financial newsletters, and IR teams used to rely on for insider-trading signals — IEX Cloud being the most prominent — have either been shut down, gated behind enterprise contracts, or degraded into licensing puzzles. The SEC publishes every Form 4 within two business days of an insider transaction, but the raw EDGAR feed isn't something you want to parse yourself. I built the infrastructure I wished existed.

How we source and parse the data

Every record traces back to a public filing on the SEC's EDGAR system — Form4API adds no opinions to the data, only structure. The pipeline, end to end:

  • Ingestion. New Form 4 filings are ingested in real time from EDGAR's getcurrent feed — typically available in the API within about a minute of SEC acceptance — while Form 144 and 13F-HR are polled on a ~10-minute cycle. Live filings move through a priority queue and a separate worker pool backfills history.
  • Parsing. Each filing's XML is parsed into structured transactions — Table I (non-derivative) and Table II (derivative) rows — with transaction codes, share counts, prices, and post-trade balances normalised into typed fields.
  • Amendment handling. A Form 4/A amendment supersedes the record it corrects; superseded transactions are flagged and excluded from queries by default, so a corrected filing is never double-counted.
  • Entity resolution. Filings are joined to company (ticker / CIK) and insider identities, and 13F-HR holdings are mapped from CUSIP to ticker — so you query by symbol, not by raw EDGAR identifiers.
  • Enrichment. Open-market trades are scored: post-trade returns at 1-day, 1-week, 1-month, 3-month, and 6-month horizons; Rule 10b5-1 plan trades detected and flagged; cluster buy/sell signals derived from coordinated insider activity; and an MSPR-style monthly sentiment score computed from 10b5-1-clean open-market flow.

The filter grammar that exposes all of this is documented in the screener guide, and the methodology behind each signal is broken down across the guides.

Why trust this with your pipeline

  • Production-grade ingestion — real-time Form 4 from EDGAR's getcurrent feed (Form 144 / 13F-HR on a ~10-minute poll), with priority queues for live filings and a separate worker pool for historical backfill.
  • 400+ backend tests (xUnit + Postgres integration suite) covering parsing, scoring, dispatch, and authorization. Test count and pass status surfaced internally on every deploy.
  • Stack is deliberately conservative: .NET 9 + PostgreSQL 16 on a single Hetzner CX23 dedicated host. Docker Compose for the runtime. No serverless gymnastics for the backend; the frontend ships on Vercel. Cheap, observable, fast to debug.
  • Open-source clients you can audit: MCP server, Sheets add-on, npm SDK, PyPI SDK.
  • Free tier exists because I was tired of API products that gate "free" behind a credit card. 15,000 requests/month (500/day), one read-only webhook, no card on file. Pricing.

Contact

Email: support@form4api.com. I read everything that comes through and reply within 24 hours on weekdays — slower on weekends.

Bug reports, feature requests, and integration questions on the open-source surface area are best filed as GitHub Issues — that's the channel I monitor most actively:

Legal

Form4API is operated independently from Sweden. Governing law for the API service is Sweden, with disputes venued in the courts of Stockholm — see the Terms of Service for the full statement. A formal business entity will be registered once the project moves out of the pre-revenue stage; this page will be updated with the registered name and Swedish organisationsnummer at that point.

Form4API is not affiliated with, endorsed by, or associated with the U.S. Securities and Exchange Commission (SEC) or EDGAR. All data is sourced from publicly available EDGAR filings. Not investment advice.