The Complete Guide to Market Data APIs for Developers

Real-time market data is the backbone of every trading, brokerage, and analytics product, yet getting clean, low-latency data is harder than it should be. Raw exchange feeds and the consolidated tape are low-level, expensive to license, and fragmented across dozens of venues. You end up parsing binary protocols, normalizing symbology, and stitching together stocks, options, and crypto from separate vendors just to render a single quote.

This guide covers every approach to getting market data as a developer: from raw exchange feeds to enriched REST APIs to real-time WebSocket streams, across stocks, ETFs, options, crypto, and prediction markets. By the end, you'll know which approach fits your use case, where the tradeoffs are, and how to pull live data with working code.

The Market Data Landscape

Before diving into code, it helps to understand the four categories of market-data providers. Each serves a different need, and most production apps end up using more than one.

Raw exchange & consolidated feeds (direct). The foundation. Direct feeds from exchanges and the consolidated tape give you every quote and trade, but you handle the parsing, normalization, and aggregation yourself. Licensing is expensive and the protocols are low-level. No adjusted history. No cross-venue best bid/offer out of the box. No options analytics.

Single-asset-class vendors. Providers that specialize in one slice, such as equities-only or options-only APIs. Great depth in their lane, but you need a separate integration (and separate symbology) the moment you add another asset class.

Multi-asset data APIs (Elgon, Polygon.io, Finnhub). Enriched data across stocks, ETFs, options, crypto, and prediction markets through one API. Production-ready: normalized quotes, adjusted OHLCV, corporate actions, and aggregated volume.

Reference & aggregator APIs (Alpha Vantage, Twelve Data). Broad symbol coverage and reference data over REST, usually with delayed quotes on lower tiers. Good for research and dashboards, less suited to sub-second trading UIs.

The right choice depends on what you're building. A simple watchlist app can get by with a delayed REST feed. A trading terminal needs enriched data with sub-second freshness. A cross-asset portfolio tracker needs a provider that covers stocks, options, and crypto behind one schema.

Raw Exchange Feeds: The Foundation (and Its Limits)

Every market-data tool ultimately builds on raw exchange and consolidated tape data. Understanding what it gives you, and what it doesn't, is essential for choosing the right approach.

What raw feeds give you

• Quotes and trades: every bid, ask, and print from the venues you license
• Order book updates: level 1 and, where licensed, full depth of book
• Market status: halts, auctions, and session transitions
• Reference identifiers: raw symbols and venue codes
• Timestamps: exchange sequence and as-of times

For a single venue and a single asset class, raw feeds are complete and authoritative.

What raw feeds do NOT give you

This is where most developers hit a wall:

• A consolidated view. A national best bid/offer across venues is something you compute yourself from every feed you license.
• Adjusted history. Splits, dividends, and symbol changes are not applied for you; you back-adjust every series.
• OHLCV bars. No aggregated candles. You build them from raw trades at every resolution you need.
• Options analytics. Greeks, implied volatility, and full chains are derived, not delivered.
• Cross-asset normalization. Equities, options, and crypto arrive in different formats with different symbology.
• Corporate actions & reference data. Issuer, sector, and entity context live outside the price feed entirely.

Cost and rate limits

Direct feeds carry exchange licensing fees, and delayed public endpoints are heavily throttled. You'll hit limits quickly under any real workload, and the cost of running your own normalization pipeline adds up fast when all you wanted was a clean quote.

When raw feeds alone are enough

• Single-venue, single-asset-class applications
• Reading the current quote or last trade for one instrument
• Latency-sensitive systems already licensed for direct feeds
• Compliance use cases that require the unmodified tape

When you need something more

• Anything that spans multiple venues or asset classes
• Charts, analytics, or adjusted historical data
• Options chains, greeks, or implied volatility
• Real-time streams without operating your own feed handlers
• Symbol search and reference data

If your app needs any of the above, you need an enriched market-data layer on top of the raw feeds.

Getting Real-Time Quotes

Quotes are the most common market-data need, and the most misunderstood. There are three ways to get a real-time quote, and they differ wildly in effort and reliability.

Option A: Normalize raw feeds yourself (painful)

License each venue, run a feed handler per protocol, compute the consolidated best bid/offer, and back-adjust history for splits and dividends. Repeat for options and crypto with their own formats. Rebuild it every time a venue changes its protocol. This is fragile, slow, and a maintenance burden most teams underestimate.

Option B: Delayed REST vendor (simple but stale)

Aggregator APIs like Alpha Vantage return quotes over REST, but the data is delayed on lower tiers and rate limits are tight. Fine for research and end-of-day dashboards; not fast enough for a live trading UI.

Option C: Elgon API (delayed REST)

The Elgon API returns quotes for any US-listed stock or ETF and supported crypto pairs through one endpoint. One request, many symbols. Quotes are real market data but delayed, tagged "source":"live" — not a real-time feed.

Here's how to get quotes for AAPL, TSLA, and SPY in a single request — no SDK, just an HTTP GET:

const res = await fetch(
  "https://elgonrpc.xyz/api/v1/quotes?symbols=AAPL,TSLA,SPY&key=elgon_sandbox_pub"
);
const { data, source } = await res.json();

console.log(data);
// data[]: { symbol, price, bid, ask, volume, asOf } for AAPL, TSLA, SPY. One request, three symbols.

Each quote carries a signed, timestamped receipt, so you can verify the data was served as-of a specific time and hasn't been altered. You can request up to 100 symbols per call.

Looking up instruments

The instruments endpoint resolves a search term into matching symbols and reference data — useful for building tickers, autocomplete, or confirming a symbol before you request quotes. Like quotes, it returns real (delayed) data, tagged "source":"live":

const res = await fetch(
  "https://elgonrpc.xyz/api/v1/instruments?q=apple&key=elgon_sandbox_pub"
);
const { data } = await res.json();

// Each match: { symbol, name, type, exchange, assetClass }
console.log(data[0]); // { symbol: "AAPL", name: "Apple Inc.", exchange: "NASDAQ", ... }

Pass any search term as q — a ticker, a company name, or a partial match. Pair it with the quotes endpoint to go from a user's search box to a live (delayed) price in two requests.

Options and Prediction Data (Sandbox)

Alongside quotes and instruments, Elgon exposes two more endpoints: options for options chains and predictions for prediction-market snapshots. Both return simulated sample data, always tagged "source":"sandbox". They are built for developing and testing your integration — do not trade or report on them as real.

An options chain for a symbol:

const res = await fetch(
  "https://elgonrpc.xyz/api/v1/options?symbol=AAPL&key=elgon_sandbox_pub"
);
const { data, source } = await res.json(); // source: "sandbox"
console.log(data.chain[0]); // { strike, type, bid, ask, iv, oi, expiry }

Prediction markets follow the same shape via /api/v1/predictions?q=fed, returning yes/no prices, volume, and close dates — simulated, for building against. Quotes and instruments remain the real (delayed) data.

Keeping Quotes Fresh with Polling

Elgon is a REST API. Every endpoint is a plain HTTP GET — there is no WebSocket, webhook, or streaming channel. Quotes are real market data but delayed, so the right pattern is to poll on an interval that fits your rate limit and your use case.

For a dashboard, screener, or watch-and-alert bot reacting on the scale of seconds to minutes, polling is exactly the right tool. Batch several symbols into one request to stay well under your limit.

Polling for quote updates

// Elgon is REST-only. Poll on an interval — there is no WebSocket.
const SYMBOL = "AAPL";

async function poll() {
  const res = await fetch(
    `https://elgonrpc.xyz/api/v1/quotes?symbols=${SYMBOL}&key=elgon_sandbox_pub`
  );
  const { data } = await res.json();
  console.log(`${SYMBOL} last: $${data[0].price} @ ${data[0].asOf}`);
}

setInterval(poll, 15000); // 4 req/min — well under the 60/min free limit

Each response carries a signed, timestamped receipt, whether you request quotes, instruments, options, or predictions. The free tier allows 60 requests/min; Growth raises it to 600/min. Because quotes are delayed, polling every few seconds is the right cadence — Elgon is not a low-latency execution feed and does not claim to be.

For a worked example, see our guide on how to build a market-watching bot, which covers polling, signals, and alerting on Elgon end to end.

New Listings and IPO Data

New listings are among the highest-interest, hardest-to-source events in the market. If you're building a screener, alerting tool, or analytics dashboard focused on fresh tickers, you need new-listing data the moment it goes live.

There's no single public feed for upcoming IPOs and new listings. Elgon indexes new-listing and IPO events directly from exchange and regulatory sources in real time, including:

• New listings and IPOs (symbol, issuer, first-trade date)
• Real-time quotes from the opening auction onward
• Direct listings and transfers between venues
• Trading activity and reference data for any newly listed security

Elgon covers new listings across major US exchanges, plus new crypto pairs as they go live on supported venues.

For the full walkthrough with working code for detecting new listings by polling the instruments endpoint, see the dedicated new-listings and IPO data guide.

Comparing Market Data Providers

Here's how the main options stack up for market-data development:

A few notes on this table:

Alpha Vantage offers broad symbol coverage and reference data over a simple REST API, with delayed quotes on lower tiers. It's strong for research and end-of-day analytics; less suited to sub-second trading UIs.

Polygon.io has solid real-time coverage of US stocks, options, and crypto with a developer-friendly API. Where it stops short is cross-asset breadth (prediction markets) and verifiable data receipts.

Elgon covers the enriched market-data layer: real-time quotes, adjusted OHLCV, options chains, ownership and corporate actions, and prediction-market data, all behind one schema, with signed, timestamped, tamper-evident receipts backed by an SLA. The multi-asset angle matters if you plan to grow beyond a single asset class.

For a broader comparison across market-data providers, see the best market data APIs comparison.

Getting Started

The right starting point depends on what you're building:

If you need raw, single-venue data and hold the exchange licenses: direct feeds are the most authoritative source.

If you need research-grade reference data: Alpha Vantage or Twelve Data. Broad coverage over REST, with delayed quotes on lower tiers.

If you need enriched, real-time, cross-asset data (quotes, charts, options, ownership, prediction markets): Elgon or Polygon.io. Elgon adds signed data receipts and a single schema across every asset class.

Quick start with Elgon

No SDK to install — make your first call in under a minute with the public sandbox key:

curl "https://elgonrpc.xyz/api/v1/quotes?symbol=AAPL&key=elgon_sandbox_pub"

// Same call in JavaScript
const res = await fetch(
  "https://elgonrpc.xyz/api/v1/quotes?symbol=AAPL&key=elgon_sandbox_pub"
);
const { data } = await res.json();
console.log(data[0]); // { symbol: "AAPL", price, bid, ask, ... }

Get a free API key at elgonrpc.xyz. The free tier is enough to build and test any market-data integration. Full API reference is at the docs.

FAQ

How do I get a real-time stock quote via API?

Use the quotes endpoint with the ticker symbol. The Elgon API returns quotes for any US-listed stock or ETF and supported crypto pair, each with a signed, timestamped receipt. Quotes are real but delayed; options and predictions are sandbox-simulated. You can request up to 100 symbols in a single call.

What is the best market data API for developers?

It depends on your use case. For research-grade reference data over REST, Alpha Vantage and Twelve Data are strong. For enriched, real-time data across stocks, options, crypto, and prediction markets, Elgon provides broad coverage of real but delayed quotes with verifiable data receipts. See our full API comparison for a detailed breakdown.

What is the difference between a raw feed and a data API?

A raw exchange feed gives you every quote and trade for the venues you license, but no consolidated view, adjusted history, or analytics. A data API like Elgon normalizes that raw data and enriches it into production-ready formats: real-time quotes, adjusted OHLCV, options chains, ownership, and corporate actions. Raw feeds are like reading unindexed log files; a data API is like querying a well-structured, indexed database.

Is there a free market data API?

Direct exchange feeds are licensed and paid, but several vendors offer free tiers with delayed or rate-limited data. Elgon offers a free tier that includes enriched market data: quotes, charts, ownership, and reference data. It's enough to build and test a real application.

How do I get institutional ownership for a stock via API?

Use the ownership endpoint with the ticker symbol. Elgon returns institutional holders (from 13F filings) with share counts and USD values. In the crypto lane, the same endpoint returns on-chain token holders. You can paginate through the full list.

Get a free Elgon API key at elgonrpc.xyz. Real-time market data across stocks, ETFs, options, crypto, and prediction markets, through one API.