Interactive Guide

The Anatomy of a Trade

An interactive journey through market microstructure: watch orders become prices, feel the spread respond to stress, and discover why these mechanics shape every trade you will ever make.

Scroll to begin▼

Chapter 01

The Order Book Comes Alive

Every market starts with two opposing lines: buyers and sellers, stacked by price and size. The order book is not just a record — it is the market's living, breathing state.

Imagine a room where buyers line up on the left and sellers on the right. The person at the front of each line sets the best bid and best ask. The gap between them is the spread. When a buyer gets impatient and crosses over to the seller's side at their price, a trade happens.

Live Order Book

MID 98.55SPR 0.50

100.204.23

100.105.69

98.801.66

98.703.55

spread 0.50

98.203.41

98.1014.00

98.006.28

97.404.03

Price levels in the live order book

Total quantity available at this price

Size:10.0

Try a large size (10+) and watch the spread blow out

Mid Price

BuySell

Try placing a market buy with a large size. Watch how the order eats through the ask side, consuming liquidity level by level. The spread widens. The midprice shifts. This is in its most elemental form.

Biais, Hillion & Spatt (1995) showed that the shape of the order book — not just the best price — contains predictive information about future price dynamics. The distribution of depth across levels reveals strategic positioning before it shows up as obvious price moves.

Chapter 02

The Price of Uncertainty

The spread is not just a cost — it is a risk price. Market makers set it wide when they're nervous, like a store charging more for something they're not sure they can restock.

Huang & Stoll (1997) decomposed the spread into three components: adverse selection (the risk of trading against someone who knows more), inventory holding (the risk of being stuck with a position), and order processing (the cost of doing business). Drag the slider below and watch all three shift in real time.

Spread Stress TestNormal

BID

11.0 bps

ASK

Market Uncertainty25%

Spread Decomposition (Huang & Stoll)

Adverse selection 38%Inventory 24%Processing 39%

Active Market Makers

7 of 8 still quoting

Notice how market makers withdraw as uncertainty rises. In crisis conditions, only one or two remain — and they demand a massive spread to compensate. A 2 bps average spread that was actually 0.5 bps for 55 seconds and 8 bps for 5 seconds tells a fundamentally different story than a steady 2 bps. The itself predicts future return volatility.

A widening spread is a leading indicator — it signals increased uncertainty about fair value before the price itself visibly reacts. Spread compression signals confident competition among liquidity providers and a regime where execution is cheaper and mean reversion is more reliable.

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Flow Metrics

Directional order flow split by taker buy vs. sell, broken into small/medium/large notional segments, with a flow toxicity score.

Code API Docs Try It

Need the ticks behind this metric? Prime + Raw includes raw trades.

volume_delta_notional

Volume Delta Notional

Volume Delta Notional shows the signed difference between aggressive buy and sell notional in the bar, making it one of the cleanest ways to spot net pressure.

Large positive readings usually mean buyers lifted offers with size, while large negative readings point to decisive sell-side aggression.

flow_toxicity_score

Flow Toxicity Score

Flow Toxicity Score combines abnormal notional imbalance with short-horizon realized volatility to highlight bars that were both one-sided and destabilizing.

The metric is designed to surface moments when liquidity providers are most likely trading against informed or urgent flow rather than routine noise.

flow_entropy

Flow Entropy

Flow Entropy measures how evenly buy and sell notional was distributed inside the interval.

High entropy suggests a balanced tug-of-war, while low entropy points to more concentrated and decisive flow in one direction.

taker_buy_sell_ratio

Buy/Sell Ratio

Buy/Sell Ratio compares aggressive buy notional to aggressive sell notional in one simple number.

It gives a fast read on whether the tape leaned meaningfully toward buyers or sellers without requiring any additional transformation.

taker_buy_large_order_percentage

Buy Large Order %

Buy Large Order % isolates how much of total aggressive buy notional came from the largest trade-size bucket.

When this rises alongside positive delta, it often suggests participation from larger and more intentional actors rather than fragmented retail flow.

Order flow tells you direction. Realized volatility tells you uncertainty. Separately, each is informative. Together, they capture something neither can alone: the toxicity of the trading environment for liquidity providers.

Endpoint

/api/v1/data/flow

Query Parameters

timestampreqstring

string

Timestamp source. 'exchange' uses the exchange-reported timestamp, 'true' uses actual arrival time at our servers.

exchangetrue

intervalreqstring

string

Aggregation time interval for the data. Sub-minute intervals (15s, 30s) require a Tier 3 subscription.

15s30s1m5m15m30m1h4h1d

exchangereqstring

string

Source exchange for the data.

binance-futuresokx-perpshyperliquid-perps

symbolreqstring

string

Trading pair symbol in the format of Atlas' universal symbology: https://github.com/aperiodic-io/atlas

start_datereqstring<date>

string<date>

Start date for the data range (YYYY-MM-DD format). Data is partitioned by year and month.

end_datereqstring<date>

string<date>

End date for the data range (YYYY-MM-DD format). Must be greater than or equal to start_date.

Successful response with download URLs for every file covering the range — one per month before 2026-08-01, one per day from 2026-08-01 onwards

Schema

filesobject[]required

Files covering the requested date range, in chronological order. Data before 2026-08-01 is split by month (one file per calendar month, no `day`); data from 2026-08-01 onwards is split by day (one file per calendar day, with `day` set). The changeover falls on a month boundary, so a given month is served entirely one way or the other; a range spanning it returns the earlier months as monthly files followed by a daily file per day.

yearintegerrequired

Year of the data file

monthintegerrequired

Month of the data file (1-12)

dayinteger

Day of the data file (1-31). Present only on daily files, i.e. those covering 2026-08-01 onwards. Absent on monthly files, which cover an entire calendar month.

urlstring<uri>required

Presigned URL for direct file download (valid for 5 minutes). URLs are served from dataset-specific subdomains, e.g. ohlcv.aperiodic.io, trade-metrics.aperiodic.io, l1-metrics.aperiodic.io, l2-metrics.aperiodic.io, derivative-metrics.aperiodic.io.

Example

{
  "files": [
    {
      "year": 2026,
      "month": 6,
      "url": "https://ohlcv.aperiodic.io/binance-futures/1h/BTCUSDT/2026-06.parquet?X-Amz-Expires=300&..."
    },
    {
      "year": 2026,
      "month": 7,
      "url": "https://ohlcv.aperiodic.io/binance-futures/1h/BTCUSDT/2026-07.parquet?X-Amz-Expires=300&..."
    },
    {
      "year": 2026,
      "month": 8,
      "day": 1,
      "url": "https://ohlcv.aperiodic.io/binance-futures/1h/BTCUSDT/2026-08-01.parquet?X-Amz-Expires=300&..."
    },
    {
      "year": 2026,
      "month": 8,
      "day": 2,
      "url": "https://ohlcv.aperiodic.io/binance-futures/1h/BTCUSDT/2026-08-02.parquet?X-Amz-Expires=300&..."
    }
  ]
}

Try It

Prefilled with the shared DEMO-KEY and a free preview slice — send the request to see live data, no account required.

timestamp*

interval*

exchange*

symbol*

Suggestions shown — any valid value accepted

start_date*

Suggestions shown — any valid value accepted

end_date*

Suggestions shown — any valid value accepted

Authentication

X-API-KEY*

GET

/api/v1/data/preview/flow?timestamp=exchange&interval=5m&exchange=binance-futures&symbol=perpetual-BTC-USDT%3AUSDT&start_date=2025-05-01&end_date=2025-05-31

Response will appear here

Interactive Guide

The Anatomy of a Trade

An interactive journey through market microstructure: watch orders become prices, feel the spread respond to stress, and discover why these mechanics shape every trade you will ever make.

Scroll to begin▼

Chapter 01

The Order Book Comes Alive

Every market starts with two opposing lines: buyers and sellers, stacked by price and size. The order book is not just a record — it is the market's living, breathing state.

Live Order Book

MID 98.55SPR 0.50

100.204.23

100.105.69

98.801.66

98.703.55

spread 0.50

98.203.41

98.1014.00

98.006.28

97.404.03

Price levels in the live order book

Total quantity available at this price

Size:10.0

Try a large size (10+) and watch the spread blow out

Mid Price

BuySell

Chapter 02

The Price of Uncertainty

The spread is not just a cost — it is a risk price. Market makers set it wide when they're nervous, like a store charging more for something they're not sure they can restock.

Spread Stress TestNormal

BID

11.0 bps

ASK

Market Uncertainty25%

Spread Decomposition (Huang & Stoll)

Adverse selection 38%Inventory 24%Processing 39%

Active Market Makers

7 of 8 still quoting

Next Chapter Soon

Register to be notified when the next chapter is available

Flow Metrics

Directional order flow split by taker buy vs. sell, broken into small/medium/large notional segments, with a flow toxicity score.

Code API Docs Try It

Need the ticks behind this metric? Prime + Raw includes raw trades.

volume_delta_notional

Volume Delta Notional

Volume Delta Notional shows the signed difference between aggressive buy and sell notional in the bar, making it one of the cleanest ways to spot net pressure.

Large positive readings usually mean buyers lifted offers with size, while large negative readings point to decisive sell-side aggression.

flow_toxicity_score

Flow Toxicity Score

Flow Toxicity Score combines abnormal notional imbalance with short-horizon realized volatility to highlight bars that were both one-sided and destabilizing.

The metric is designed to surface moments when liquidity providers are most likely trading against informed or urgent flow rather than routine noise.

flow_entropy

Flow Entropy

Flow Entropy measures how evenly buy and sell notional was distributed inside the interval.

High entropy suggests a balanced tug-of-war, while low entropy points to more concentrated and decisive flow in one direction.

taker_buy_sell_ratio

Buy/Sell Ratio

Buy/Sell Ratio compares aggressive buy notional to aggressive sell notional in one simple number.

It gives a fast read on whether the tape leaned meaningfully toward buyers or sellers without requiring any additional transformation.

taker_buy_large_order_percentage

Buy Large Order %

Buy Large Order % isolates how much of total aggressive buy notional came from the largest trade-size bucket.

When this rises alongside positive delta, it often suggests participation from larger and more intentional actors rather than fragmented retail flow.

Endpoint

/api/v1/data/flow

Query Parameters

timestampreqstring

string

Timestamp source. 'exchange' uses the exchange-reported timestamp, 'true' uses actual arrival time at our servers.

exchangetrue

intervalreqstring

string

Aggregation time interval for the data. Sub-minute intervals (15s, 30s) require a Tier 3 subscription.

15s30s1m5m15m30m1h4h1d

exchangereqstring

string

Source exchange for the data.

binance-futuresokx-perpshyperliquid-perps

symbolreqstring

string

Trading pair symbol in the format of Atlas' universal symbology: https://github.com/aperiodic-io/atlas

start_datereqstring<date>

string<date>

Start date for the data range (YYYY-MM-DD format). Data is partitioned by year and month.

end_datereqstring<date>

string<date>

End date for the data range (YYYY-MM-DD format). Must be greater than or equal to start_date.

Successful response with download URLs for every file covering the range — one per month before 2026-08-01, one per day from 2026-08-01 onwards

Schema

filesobject[]required

yearintegerrequired

Year of the data file

monthintegerrequired

Month of the data file (1-12)

dayinteger

Day of the data file (1-31). Present only on daily files, i.e. those covering 2026-08-01 onwards. Absent on monthly files, which cover an entire calendar month.

urlstring<uri>required

Example

{
  "files": [
    {
      "year": 2026,
      "month": 6,
      "url": "https://ohlcv.aperiodic.io/binance-futures/1h/BTCUSDT/2026-06.parquet?X-Amz-Expires=300&..."
    },
    {
      "year": 2026,
      "month": 7,
      "url": "https://ohlcv.aperiodic.io/binance-futures/1h/BTCUSDT/2026-07.parquet?X-Amz-Expires=300&..."
    },
    {
      "year": 2026,
      "month": 8,
      "day": 1,
      "url": "https://ohlcv.aperiodic.io/binance-futures/1h/BTCUSDT/2026-08-01.parquet?X-Amz-Expires=300&..."
    },
    {
      "year": 2026,
      "month": 8,
      "day": 2,
      "url": "https://ohlcv.aperiodic.io/binance-futures/1h/BTCUSDT/2026-08-02.parquet?X-Amz-Expires=300&..."
    }
  ]
}

Try It

Prefilled with the shared DEMO-KEY and a free preview slice — send the request to see live data, no account required.

timestamp*

interval*

exchange*

symbol*

Suggestions shown — any valid value accepted

start_date*

Suggestions shown — any valid value accepted

end_date*

Suggestions shown — any valid value accepted

Authentication

X-API-KEY*

GET

/api/v1/data/preview/flow?timestamp=exchange&interval=5m&exchange=binance-futures&symbol=perpetual-BTC-USDT%3AUSDT&start_date=2025-05-01&end_date=2025-05-31

Response will appear here