Get free US-stock fundamentals from the SEC EDGAR API (and build a "divergence score")

You want revenue, net income, and EPS for US stocks — free, no API key, no flaky scraping. Good news: the SEC hands you the actual filings in machine-readable form via the EDGAR companyfacts API. Here's how to pull fundamentals, the gotchas that will bite you, and how to turn it into a simple "is this stock rich or cheap?" signal.

Why SEC EDGAR

• Official, primary source — the exact 10-K (annual) / 10-Q (quarterly) filings. Accurate numbers.
• No key, free, commercial-ok — generous rate limits (you must send a descriptive User-Agent).
• Structured — XBRL tags (US-GAAP) let you pull "revenue", "net income", etc. by concept name.

Prices aren't in EDGAR, so pair it with a price source (stooq, Yahoo-style feeds, etc.).

1. Resolve the CIK

EDGAR keys companies by CIK (a serial ID), not ticker. Grab the mapping:

curl -s -H "User-Agent: your-app your@email" \
  https://www.sec.gov/files/company_tickers.json

Look up your ticker, then zero-pad the CIK to 10 digits (320193 → 0000320193).

2. Pull companyfacts

curl -s -H "User-Agent: your-app your@email" \
  https://data.sec.gov/api/xbrl/companyfacts/CIK0000320193.json

Under facts."us-gaap" you get a time series per concept. The useful ones:

Each value sits in units.USD (or USD/shares for EPS) with start/end (period), fp (Q1–FY), form (10-K/10-Q), and fy. Different companies use different tags for the same thing (some report Revenues, others RevenueFromContractWithCustomer…), so try a prioritized list of candidate tags.

const CANDIDATES = {
  revenue: ['RevenueFromContractWithCustomerExcludingAssessedTax', 'Revenues', 'SalesRevenueNet'],
  netIncome: ['NetIncomeLoss'],
  epsDiluted: ['EarningsPerShareDiluted'],
};
const pick = (facts, keys, unit = 'USD') => {
  for (const k of keys) {
    const u = facts['us-gaap']?.[k]?.units?.[unit];
    if (u?.length) return u;
  }
  return null;
};

3. Gotchas (this is the real work)

① Quarterly values are year-to-date — diff them

10-Q revenue is often reported cumulatively (YTD), not as a standalone quarter. To get Q3's three months: Q3 YTD − Q2 YTD. Q1 is as-is; Q4 = annual (10-K) − sum(Q1..Q3). Naively summing YTD figures double-counts and doubles your revenue.

② Splits make EPS and price jump

Historical EPS and price show step changes around splits. For time-series comparison you need split adjustment (using adjusted-close on the price side is the easy path).

③ US-GAAP only → foreign filers are missing

companyfacts us-gaap covers US-basis filers (10-K/10-Q). Foreign companies file 20-F / IFRS and won't appear here. "Why can't I get TSM or ASML?" — that's why.

④ Use TTM

Quarters are seasonal, so for P/E and P/S use trailing-twelve-months (sum of the last 4 quarters).

4. Combine with price → a "divergence score"

Once you have fundamentals (the reality) and price (the expectation), a fun signal falls out. I use divergence = price CAGR − revenue CAGR:

divergence = CAGR(price) − CAGR(revenue)
  CAGR(x) = (x_end / x_start) ** (1 / years) − 1

• price growing faster than revenue → expectations have run ahead of the business (rich-leaning)
• the reverse → the business is outpacing the price (cheap-leaning)

Layer in P/E and P/S versus each stock's own historical range (median, 25–75% band) and you get a neutral "is this high or low for this stock?" read that's harder to misread than an absolute P/E.

A worked example

I built a free visualizer around exactly this — kabu — that shows the price-vs-fundamentals gap for US stocks using only EDGAR + prices (e.g. the NVDA read). It's Japanese-first with an English UI, and it gives no investment advice — just a neutral, sourced visualization.

Wrap-up

• US-stock fundamentals are free and official via SEC EDGAR companyfacts.
• The gotchas that matter: quarterly = YTD diff / split adjustment / US-GAAP only (no foreign) / TTM.
• Pair with price for a divergence score to see expectation vs reality.

Start with one ticker: hit companyfacts, list Revenues, and plot it. The rest is bookkeeping.

Based on public SEC filings and public prices. This post (and the tool mentioned) is for information/education, not investment advice.