FilingFirehose Blog

Original research, SEC-filings how-tos, and quant-style observations. Updated daily.

• Building Real-Time SEC Filing Webhook Alerts
  2026-07-25
  

  RSS feeds, REST APIs, and WebSockets each offer different latency and reliability tradeoffs for monitoring SEC filings. Here's how to pick the right stack for your strategy.

• Classifying 8-K Bodies: Why Filer-Reported Items Aren't Enough
  2026-07-24
  

  Standard 8-K item codes miss critical disclosures buried in body text. Our analysis found 7.3% misclassification rates when filers choose wrong items, creating blind spots for SEC researchers and quants.

• Working with SEC EDGAR XBRL Data: A Tutorial
  2026-07-23
  

  XBRL submissions unlock machine-readable SEC filings, but parsing them requires understanding concept mappings, validation rules, and the EDGAR API. Here's how to extract structured financial data correctly.

• How to Parse SEC EDGAR Filings with Python
  2026-07-22
  

  Extract structured financial data directly from SEC EDGAR filings using Python, requests, BeautifulSoup, and Polars for fast, reproducible analysis.

• SEC EDGAR API Rate Limits: What You Need to Know
  2026-07-21
  

  The SEC's EDGAR API enforces a 10 req/s/IP rate limit. Learn how to detect 429 errors, implement exponential backoff, and scale across multiple IPs without hitting compliance walls.

• Land and Buildings: REIT-Focused Activism
  2026-07-20
  

  Activists are increasingly targeting REITs through Section 13(d) filings and proxy campaigns, exploiting operational inefficiencies and capital allocation gaps unique to the property sector.

• Sachem Head: Activist Filings and Targets
  2026-07-19
  

  Sachem Head's activist campaigns reveal patterns in mid-cap targeting. A filing-level analysis of disclosure timing, holding thresholds, and campaign mechanics.

• Blue Orca Capital: Short-Seller Research and Filings
  2026-07-18
  

  Short-sellers like Blue Orca Capital mine SEC filings for red flags. We break down their research playbook, the form types they target, and how quant traders can use the same techniques.

• Karpus Investment Management: Activist History
  2026-07-17
  

  Karpus Investment Management has quietly accumulated significant stakes in closed-end funds over the past decade, often filing Schedule 13D disclosures with specific reform agendas rarely covered by mainstream financial

• Bulldog Investors: 13D Filings on Closed-End Funds
  2026-07-16
  

  13D filings on closed-end funds reveal activist pressure on illiquid securities. Understanding the nuances separates signal from noise in fund activism.

• Saba Capital: Closed-End Fund Activism Filings
  2026-07-15
  

  Saba Capital's CEF activism filings reveal a systematic playbook for targeting closed-end fund discounts, with high-signal 13D patterns that quant investors can monitor via SEC Edgar.

• ValueAct Capital: Constructive Activism via 13D
  2026-07-14
  

  ValueAct Capital pioneered a stealth activism model using Schedule 13D disclosures to build influential stakes while avoiding public campaigns. How they gamed SEC rules and what it means for quants.

• Trian Fund Management: Peltz Activist Filings
  2026-07-13
  

  Trian Fund Management's activist campaigns, from P&G to Mondelez, hinge on proxy contests and 13D filings. Here's how to parse the SEC disclosures that signal board-seat pushes.

• Third Point Activism: Loeb's 13D Pattern
  2026-07-12
  

  Dan Loeb's Third Point follows a disciplined 13D workflow: file, then public amplification. This pattern has become a playbook for modern activism and reveals institutional choreography.

• JANA Partners: Activist Filings and Sector Focus
  2026-07-11
  

  JANA Partners' activist playbook centers on deep sector expertise and targeted operational fixes. Here's how their Schedule 13D filings reveal consistent thematic patterns across industrials, tech, and financials.

• Engine No. 1: ESG Activism Through 13D Filings
  2026-07-10
  

  Engine No. 1's 2021 campaign against Exxon Mobil via Schedule 13D pioneered ESG activism tactics that forced board representation. Learn how activists weaponize SEC filings to drive environmental governance changes.

• Pershing Square: Reading Bill Ackman's 13D Filings
  2026-07-09
  

  How to extract exit signals and activism timing from Bill Ackman's Schedule 13D filings. A quant guide to reading disclosure patterns at Pershing Square.

• Elliott Management 13D Filings: The Playbook
  2026-07-08
  

  Elliott Management's 13D filings reveal a systematic playbook: acquisition timing, stake sizing, board demand letters, and follow-through amendments. Decoding the pattern helps investors anticipate activist pressure.

• Starboard Value: How They File and Why It Matters
  2026-07-07
  

  Starboard Value's filing strategy reveals activist pressure tactics through Schedule 13D patterns, SEC item codes, and campaign timing. Here's how to decode their moves for early signals.

• Icahn Enterprises: 13D Filings Pattern Over 10 Years
  2026-07-06
  

  Tracking Carl Icahn's 13D filings across a decade reveals patterns in disclosure timing, stake accumulation strategy, and regulatory arbitrage that quant researchers can model.

• 8-K Item 9.01: Reading Financial Statements and Exhibits
  2026-07-05
  

  SEC filers bury crucial financial data in 8-K exhibits. Learn to parse Item 9.01, map exhibit conventions, and extract edge signals before algos do.

• 8-K Item 1.05: Cybersecurity Incident Disclosures
  2026-07-04
  

  The SEC's new 8-K Item 1.05 rule mandates real-time disclosure of material cybersecurity incidents. Here's what triggers reporting, filing timelines, and what traders should monitor.

• 8-K Item 8.01: Why 'Other Events' Are Often the Most Important
  2026-07-03
  

  8-K Item 8.01 (Other Events) is where material disclosures hide in plain sight. Companies often misclassify news there to avoid triggering Item 2.02 or 8.01 strict timing, creating alpha for careful readers.

• 8-K Item 5.02: Executive Departure Filings Decoded
  2026-07-02
  

  8-K Item 5.02 filings reveal departure language patterns that signal distress or planned transitions. Learn what terms like "mutual agreement" versus "other" actually mean in executive departures.

• 8-K Item 3.01: Delisting Notices and What They Mean
  2026-07-01
  

  8-K Item 3.01 delisting notices reveal forced capital actions before public markets respond. Learn how to parse them for event-driven short opportunities.

• 8-K Item 2.05: Cost Reductions and Restructuring Charges
  2026-06-30
  

  Item 2.05 8-K filings reveal restructuring costs before earnings impact. Learn to decode disclosure patterns that signal operational stress or executive confidence shifts.

• 8-K Item 2.01: M&A Disclosure Decoded
  2026-06-29
  

  8-K Item 2.01 governs M&A disclosure: acquisitions trigger mandatory filings, but dispositions follow a higher materiality threshold. Learn when to file and what's actually required.

• 8-K Item 1.01: Material Definitive Agreements (What to Watch)
  2026-06-28
  

  8-K Item 1.01 filings flag material agreements, but most lack substance. Learn what signals a real deal versus routine boilerplate by dissecting disclosure standards and filing patterns.

• Form D Filings: Private Placement Exemptions Decoded
  2026-06-27
  

  Form D filings reveal the legal scaffold of private placements. Learn how Regulation D exemptions work, what each form field signals, and why institutional investors mine these for deal flow intelligence.

• Form 4 Filings: How to Spot Real Insider Activity
  2026-06-24
  

  Form 4 filings reveal insider trades, but most traders miss critical details. Learn to parse transaction codes, spot wash-sale patterns, and identify real signal in SEC disclosures.

• Form 424B5: How to Read a Shelf Takedown Filing
  2026-06-19
  

  Form 424B5 is the SEC's shelf-takedown prospectus supplement, filed when issuers execute secondary offerings from a registered shelf. Learn what data matters for quants tracking capital raises and equity dilution.

• Form S-3 Explained: Shelf Registrations Decoded
  2026-06-14
  

  Form S-3 shelf registrations let issuers register securities upfront and sell them later without re-filing. We decode the mechanics, eligibility rules, and why algos should care about ATM offerings.

• 10-Q vs 10-K: Key Differences for Filings Researchers
  2026-06-12
  

  10-Q and 10-K differ in frequency, audit scope, and required disclosures. Learn how to extract actionable signals from each for SEC research.

• Form 13F: What Institutional Investors Must Disclose
  2026-06-10
  

  Form 13F, filed quarterly by institutional asset managers, reveals portfolio holdings over $100M. Learn the filing rules, lag periods, and how to extract alpha from public SEC disclosures.

• Schedule 13D vs 13G: What's the Real Difference
  2026-05-31
  

  Schedule 13D and 13G both disclose major equity stakes, but the difference hinges on intent: activists file 13D; passive holders file 13G. Know which applies to your research.

• Form 8-K Filing Types Explained (All 35 Items)
  2026-05-29
  

  Complete breakdown of all 35 Form 8-K items (1.01 through 9.01). Learn which events trigger disclosure, real examples, and how to scan filings for alpha.