Providers

market-feed ships with six built-in providers. Each implements the same MarketProvider interface so you can swap or combine them without changing your application code.

Provider comparison

Provider	API Key	Quote	Historical	Search	Company	News	Fundamentals	Free tier
Yahoo Finance	No	✓	✓	✓	✓	—	✓	Unlimited (unofficial)
Alpha Vantage	Yes	✓	✓	✓	✓	—	—	25 calls/day, 5/min
Polygon.io	Yes	✓	✓	✓	✓	✓	—	5 calls/min, 15-min delay
Finnhub	Yes	✓	✓	✓	✓	✓	—	60 calls/min
Twelve Data	Yes	✓	✓	✓	✓	—	—	800 calls/day, 8/min
Tiingo	Yes	✓	✓	✓	✓	✓	—	1 000 calls/day

Get free keys: Alpha Vantage · Polygon.io · Finnhub · Twelve Data · Tiingo

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Yahoo Finance

The default provider. No API key required.

import { MarketFeed, YahooProvider } from "market-feed";

const feed = new MarketFeed({
  providers: [new YahooProvider()],
});

Options

new YahooProvider({
  timeoutMs: 10_000,  // request timeout, default 10s
  retries: 2,         // retry attempts on transient failures, default 2
});

Unique features

Yahoo is the only built-in provider that supports financial statements (income statement, balance sheet, cash flow) via market-feed/fundamentals.

Notes

• Uses the unofficial query1.finance.yahoo.com API — not endorsed by Yahoo
• Cannot run in the browser (CORS blocked) — use server-side only
• If a stock is delisted, Yahoo removes its historical data retroactively

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Alpha Vantage

Free: 25 API calls/day, 5 calls/minute. Paid plans available.

import { MarketFeed, AlphaVantageProvider } from "market-feed";

const feed = new MarketFeed({
  providers: [
    new AlphaVantageProvider({ apiKey: process.env.AV_KEY! }),
  ],
});

Options

new AlphaVantageProvider({
  apiKey: "YOUR_KEY",     // required
  timeoutMs: 10_000,
  retries: 2,
  rateLimiter: myLimiter, // override built-in rate limiter
});

Rate limiting

The built-in rate limiter enforces 5 calls/minute client-side. When the limit is hit, a RateLimitError is thrown with a retryAfter date.

If you have a premium plan, pass a custom RateLimiter:

import { RateLimiter } from "market-feed";

new AlphaVantageProvider({
  apiKey: process.env.AV_KEY!,
  rateLimiter: new RateLimiter("alpha-vantage", 75, 75 / 60), // 75/min premium
});

---

Polygon.io

Free tier: 15-minute delayed data, 5 calls/minute.

import { MarketFeed, PolygonProvider } from "market-feed";

const feed = new MarketFeed({
  providers: [
    new PolygonProvider({ apiKey: process.env.POLYGON_KEY! }),
  ],
});

Unique features

• Supports news: feed.news("AAPL")
• Supports WebSocket streaming via market-feed/ws (paid real-time plan, or delayed on free)

---

Finnhub

Free: 60 API calls/minute.

import { MarketFeed, FinnhubProvider } from "market-feed";

const feed = new MarketFeed({
  providers: [
    new FinnhubProvider({ apiKey: process.env.FINNHUB_KEY! }),
  ],
});

Unique features

• Supports news: feed.news("AAPL")
• Supports WebSocket streaming via market-feed/ws
• Supports earnings, dividends, splits

---

Twelve Data

Free: 800 API calls/day, 8 calls/minute. Good for crypto and forex in addition to stocks.

import { MarketFeed, TwelveDataProvider } from "market-feed";

const feed = new MarketFeed({
  providers: [
    new TwelveDataProvider({ apiKey: process.env.TD_KEY! }),
  ],
});

Symbol format

Twelve Data uses / as a separator for forex and crypto pairs. market-feed converts automatically:

Input	Sent to Twelve Data
BTC-USD	BTC/USD
EURUSD=X	EUR/USD
AAPL	AAPL

---

Tiingo

Free: 1 000 API calls/day. Provides adjusted close prices in historical data.

import { MarketFeed, TiingoProvider } from "market-feed";

const feed = new MarketFeed({
  providers: [
    new TiingoProvider({ apiKey: process.env.TIINGO_KEY! }),
  ],
});

Authentication

Tiingo uses Authorization: Token KEY header authentication.

Unique features

• Historical bars include adjClose (split- and dividend-adjusted)
• Supports news

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Using multiple providers

Provide an array in priority order. With fallback: true (default), market-feed tries each provider until one succeeds:

import {
  MarketFeed,
  YahooProvider,
  AlphaVantageProvider,
  PolygonProvider,
  FinnhubProvider,
  TwelveDataProvider,
  TiingoProvider,
} from "market-feed";

const feed = new MarketFeed({
  providers: [
    new YahooProvider(),                                              // free, no key
    new AlphaVantageProvider({ apiKey: process.env.AV_KEY! }),       // fallback 1
    new PolygonProvider({ apiKey: process.env.POLYGON_KEY! }),       // fallback 2
    new FinnhubProvider({ apiKey: process.env.FINNHUB_KEY! }),       // fallback 3
    new TwelveDataProvider({ apiKey: process.env.TD_KEY! }),         // fallback 4
    new TiingoProvider({ apiKey: process.env.TIINGO_KEY! }),         // fallback 5
  ],
  fallback: true,
});

Read more in Fallback & Reliability.