Every source below is genuinely free — no signup fees, no paid tiers. Sources with no published rate limit (Nasdaq, NYSE, StockAnalysis) are scraped conservatively (a few times a day, not continuously) specifically so this doesn't look like abuse to either exchange. The official APIs (Finnhub, SEC EDGAR ×3) have documented limits this pipeline stays comfortably under. A per-host circuit breaker backs a source off for 6 hours after 3 consecutive failures instead of retrying into whatever's blocking it, and robots.txt is checked before every scrape. Nasdaq's and NYSE's pages are client-rendered apps that don't return their tables to a plain fetch — those cards show as errors until an optional Playwright fallback is enabled.

delisting_type is a heuristic, not a legal determination — compliance-driven signals come mostly from the exchange non-compliance lists, M&A signals come from wire-sourced merger news and 8-K item codes, deregistration means a company filed to stop SEC reporting (Form 15) rather than being delisted by an exchange, and SEC EDGAR Forms 25-NSE/25 (SEC confirmed) are the authoritative confirmation but don't themselves state a reason.