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Reference explainers for the SEC filing forms developers, traders, and quants actually deal with. Every page is written for working professionals: no jargon, no fluff, with the API view of the data at the bottom.

• What is a Form 4 filing? (SEC insider trading disclosure)A Form 4 is the SEC filing that company insiders submit within two business days of trading their own company's stock. Here's what it contains and how to read it.
• Form 4 transaction codes (P, S, A, M, F and the rest) explainedEvery transaction code that can appear on an SEC Form 4 filing, what it means, and how seriously to read each one as a signal.
• What is a 13F filing? (Institutional holdings disclosure)A 13F is the quarterly SEC filing where institutional investment managers with over $100M in assets disclose their long equity positions. Here's what it contains, when it's filed, and how to use it.
• What is an 8-K filing? (SEC material events disclosure)An 8-K is the SEC filing that public companies use to disclose material events between quarterly reports, earnings, executive changes, acquisitions, and more. Here's what it covers and when it's filed.
• What is a 10-K filing? (SEC annual report)A 10-K is the comprehensive annual report public companies file with the SEC. Here's what it contains, when it's filed, and how it differs from a 10-Q or an annual report to shareholders.
• Complete list of SEC filing types (and what each one means)Every common SEC filing type, 10-K, 10-Q, 8-K, S-1, Form 3/4/5, 13F, 13D/G, DEF 14A, Schedule 14A, and the rest, explained in plain English with links to deeper guides.
• What is a Form 3 SEC filing? (Initial beneficial ownership statement)Form 3 is the SEC filing that new insiders submit to establish their starting ownership position. Here's who files it, when, and what it contains.
• What is a Form 5 SEC filing? (Annual insider ownership report)Form 5 is the annual SEC filing that catches exempt transactions insiders didn't have to report on Form 4 during the year. Here's what goes on it and when it's due.
• What is a Schedule 13D SEC filing? (Activist ownership disclosure)Schedule 13D is filed when an investor crosses 5% beneficial ownership with intent to influence or change control. Here's what's in it and why it moves stocks.
• What is a Schedule 13G SEC filing? (Passive 5%+ ownership disclosure)Schedule 13G is the simplified SEC filing for passive investors who cross 5% beneficial ownership. Here's who qualifies, when it's due, and when a 13G must convert to 13D.
• What is a 10-Q filing? (Quarterly report explained)A 10-Q is the unaudited quarterly financial report that public companies file with the SEC within 40-45 days of each quarter end. Here's what's in it and how to use it.
• Form 4 transaction codes explained (P, S, A, F, M, and every other code)Complete reference for SEC Form 4 transaction codes. What P, S, A, F, M, D, G, J, and every other code actually mean, with real examples and how to filter them via API.
• What is a Form S-1 filing? (IPO registration statement explained)An S-1 is the SEC registration statement required before a company can sell securities to the public in an IPO. Here's what it discloses and how the process works.
• 13F filing deadlines by quarter (2026 and beyond)Complete calendar of SEC 13F filing deadlines for institutional investors. When Berkshire Hathaway, Bridgewater, and Renaissance Technologies must file each quarter, and how to get the data via API within minutes of publication.
• Form 4 vs Form 144: what's the difference?Form 4 is filed after an insider transaction. Form 144 is filed before a planned sale of restricted or control securities. Here's how they differ and when both apply.
• Schedule 13D vs 13G: what's the difference?13D is the activist filing; 13G is the passive holder filing. Both are triggered by crossing 5% ownership, but the deadlines, content, and implications are very different.
• How real-time SEC filing APIs actually work (and why most are not real-time)The truth about SEC filing latency. Why most 'real-time' APIs are actually 12-24 hours behind, how EdgarKit hits 30 seconds, and what latency actually matters for your use case.
• How to read a Form 4 filing (line by line)A walk-through of an actual SEC Form 4 filing showing exactly what each field means and which lines actually matter for trading and research.
• CUSIP vs CIK: what each identifier means and when to use whichCUSIP identifies a specific security, CIK identifies a specific filer. Confusing them breaks half the EDGAR queries beginners write. Here's the difference, with examples.
• What is a DEF 14A filing? (Definitive proxy statement)A DEF 14A is the definitive proxy statement that public companies file before their annual meetings. It contains executive compensation, board nominees, shareholder proposals, and voting matters.
• What is Form 144? (Notice of proposed sale of restricted securities)Form 144 is the SEC notice that affiliates file before selling restricted or control securities. It is filed in advance of the sale, unlike Form 4 which is filed afterward.
• SEC EDGAR API rate limits: what they actually are (and how to work with them)The SEC publishes a 10-requests-per-second limit on EDGAR. Real-world behavior is more nuanced. Here's what you can actually get away with and how to design around the limits.
• Insider trading data: where it comes from, what it includes, how to use itA complete primer on insider trading data: which SEC filings produce it, what gets reported, common screening strategies, and how to access it programmatically.
• SEC EDGAR full-text search: what it can and can't doEDGAR's full-text search is powerful for keyword queries across millions of filings, but it has limits worth knowing before you build on top of it.