Streaming Market Data Using The Investors Exchange (IEX) API

July 13, 2018
After bench-marking APIs we've published to the API Gallery we go through each of the individual API paths and identify the ones that have the high potential for turning into real-time streams, for use in dashboards, mobile applications, training machine learning models, and other applications. After we've StreamRanked them, we publish to a special listing of APIs, and make sure we profile individually here on the blog--next on the list of valuable data APIs is the open financial trading market IEX API.

IEX was created in response to questionable trading practices that had become widely used across traditional public Wall Street exchanges as well as dark pools and other alternative trading systems. The IEX exchange aims to attract investors by promising to "play fair" by operating in a transparent and straightforward manner, while also helping to level the playing field for traders. Strategies to achieve those goals include:

- Publishing the matching rules used in the exchange's computerized order matching engine.
- Offering a limited number of simple and familiar order types.
- Charging fixed fees on most orders (or a flat percentage rate on small orders).
- Ensuring market pricing data arrives at external points of presence simultaneously.
- Slightly delaying market pricing data to all customers (no colocation).
- Refusing to pay for order flow.

These strategies are intended to ensure the trustworthiness of the exchange. A few dark pools are owned by trading companies that pay for certain types of orders to allow them to fill orders within the pool, rather than routing orders to public exchanges. IEX offers no rebates for orders,[10] and only charges a flat fee of $0.0009 per share on trades executed within the dark pool (or 0.30% with shares worth less than $1.00). Trades forwarded to other trading venues are charged a lower rate.

Key Links:

Blog RSS
Change Log
Road Map

High-Value API Paths:

Auction (GET) - For an example of an app that’s using stats, see our IEX mobile app
Book (GET) - Subscribe to the book channel
Operational Halt Status (GET) - Subscribe to the ophaltstatus channel
Security Event (GET) - Subscribe to the security event channel
HIST (GET) - HIST will provide the output of IEX data products for download on a T+1 basis
Chart (GET) - The above example will return JSON with the following keys
Market (GET) - This endpoint returns near real-time traded volume on the markets
Corporate Actions (GET) - Refer to the Daily list specification for further details
Historical Summary (GET) - See our stats page for a reference of the keys
Recent (GET) - This call will return a minimum of the last five trading days up to all trading days of the current month
Delayed Quote (GET) - This returns the 15 minute delayed market quote
News (GET) - The above example will return JSON with the following keys
Previous (GET) - This returns previous day adjusted price data for a single stock, or an object keyed by symbol of price data for the whole market
Quote (GET) - Pulls a stock quote using any ticker symbol
Short Interest List (GET) - Refer to the Short Interest specification for further details
Splits (GET) - Returns stock splits for any date range using ticker symbol
TOPS (GET) - Our eligible symbol reference is updated daily

IEX is a unique player in the market data and trading arena. They are small, but fast-growing, and different than the other players in the game. They provide a specialized look at a very volatile, dark, and often out of reach market for many average traders. Making it an honest and valuable source of data when it comes to streaming market data, and working to develop an understanding of how things are moving. Their API is free, and publicly accessible, something you can't say of other providers and exchanges.

You can find more high-value APIs in the StreamRank portion of the API Gallery, and access IEX and the hundreds of other API providers we've profiled as part of the API Gallery. Everything runs as individual Github repositories, driven by OpenAPI definitions, which makes it all forkable and integratable into your own applications and systems.

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