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Market data concepts, explained

Market Data Guides

Clear explanations of the concepts behind market data APIs, from OHLCV, tick data, quotes, trades, venues, and OTC markets to REST, WebSocket, FIX, fundamentals, fair prices, and on-chain TVL.

Learn the concept first, then see how it works inside SiftingIO.

Data concepts

What is OHLCV data?

OHLCV data sums up price and trading activity over a fixed interval into five numbers: open, high, low, close, and volume. It is the format behind every candlestick chart and most historical market analysis.

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Data concepts

Real-time vs delayed market data

Real-time market data reflects the market as it moves right now; delayed data is the same data held back by a fixed lag, often 15 minutes. The difference matters for trading, alerts, and anything where timing changes the decision.

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Data concepts

What is delayed market data?

Delayed market data is live data published after a fixed lag, commonly 15 minutes. The prices are accurate for the moment they describe, but they show where the market was, not where it is.

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Data concepts

What is end-of-day data?

End-of-day (EOD) data is a single snapshot of a market per trading session, usually the closing values. It is the lightest form of market data and the standard input for long-horizon analysis.

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Delivery

REST vs WebSocket for market data

REST is request-and-response: a client requests data and receives a snapshot. WebSocket is a persistent connection that pushes updates as they happen. Most market data products use both, each for what it does best.

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Data concepts

What is derived market data?

Derived market data is any value computed from raw prices and trades rather than observed directly: VWAP, 24-hour change, moving averages, and OHLCV bars are all derived. The distinction shows where calculation assumptions lie.

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Data concepts

What is index data?

An index condenses a group of assets into a single number that tracks their combined movement. Index data is that value together with the constituents, weights, and methodology behind it, used as a benchmark rather than a tradable instrument.

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Market structure

What is a trading venue?

A trading venue is any place where buyers and sellers meet to trade an asset. The same asset usually trades on many venues at once, which is why a single price can vary from one venue to the next.

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Market structure

What is an exchange?

An exchange is a centralized, rules-based marketplace where buy and sell orders meet in one shared order book. It is one type of trading venue, defined by transparent pricing, listing standards, and a central matching process.

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Market structure

What is an OTC market?

An over-the-counter, or OTC, market is one where two parties trade directly with each other, usually through dealers, instead of through a central exchange. Much of the world's currency, bond, and commodity trading works this way.

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Data concepts

What is an aggregated fair price?

An aggregated fair price combines quotes from many sources into a single reference price, weighted and filtered so that no individual source distorts it. It provides a stable, representative value rather than the price from a single feed.

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On-chain

What is a DEX?

A decentralized exchange (DEX) lets participants trade crypto assets directly on a blockchain through smart contracts, without a central intermediary holding funds or matching orders. Many DEXs price trades using liquidity pools rather than an order book.

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On-chain

What is TVL in DeFi?

Total Value Locked (TVL) is the dollar value of all assets deposited in a DeFi protocol. It is the most common gauge of how much capital a protocol holds, useful as a size signal but easy to misread on its own.

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Market data

What is a currency pair?

A currency pair quotes one currency against another, such as EURUSD or GBPUSD. The price says how much of the second currency, the quote, is needed to buy one unit of the first, the base.

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Market data

What is bid and ask?

The bid is the highest price buyers are willing to pay; the ask is the lowest price sellers will accept. Together they form every quote, and the difference between them is the spread.

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Market data

What is the bid-ask spread?

The spread is the difference between the bid and the ask. It indicates how liquid a market is and represents an implicit cost of trading: the narrower the spread, the lower the cost of entering and exiting.

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Market data

What is tick data?

Tick data is the stream of individual market updates, each one a single quote or trade with a price, a size, and a timestamp. It is the most granular form of market data, recorded as it happens with no aggregation.

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Market data

What is quote data?

Quote data is the stream of bid and ask updates for an asset: the prices and sizes at which participants are currently willing to buy and sell. It captures intentions to trade, separate from trades that have actually executed.

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Market data

What is trade data?

Trade data is the record of executed transactions for an asset, each entry capturing the price, size, and time of a completed trade. Unlike quotes, which show intentions, trade data shows what actually happened.

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Market data

What is previous close?

The previous close is an asset's last traded price from the prior session. It is the standard reference point for measuring daily change and for charting the gap between one session and the next.

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Market data

What is Level 1 market data?

Level 1 market data is the top-of-book view of a market: the best bid, the best ask, and the most recent trade. It is the everyday view most apps and charts run on, without the deeper order book behind it.

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Market data

What is Level 2 market data?

Level 2 market data is the depth-of-book view: multiple levels of bids and asks beyond the best price, showing the resting orders and sizes waiting on each side. It reveals liquidity that Level 1 hides.

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Market data

What is market depth?

Market depth is the volume of buy and sell orders waiting at each price around the current quote. It shows how much an asset can absorb before the price moves, and is displayed as the depth of market, or DOM.

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Data concepts

What is fundamental data?

Fundamental data describes the underlying health and characteristics of an asset, such as a company's financial statements and filings or a protocol's on-chain metrics, as opposed to its market price.

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Delivery

What is a FIX API?

FIX (Financial Information eXchange) is a long-standing messaging protocol that financial systems use to exchange market data and orders over a persistent session. It is the common language of institutional trading platforms.

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