Order Books and Market Depth Explained

Introduction

Next reading

• What Is A Betting Exchange
• Liquidity On A Betting Exchange

This article explains how the order book works on a betting exchange and how it displays available prices and volumes on both sides of a market. It also introduces the concept of market depth and explains how price levels reflect supply and demand.

It builds on the previous article about liquidity and further develops the structural understanding of exchange markets.

Definition

An order book is a real-time list of all unmatched back and lay bets at different price levels within a betting exchange market.

It shows:

• Available back prices and corresponding stake amounts
• Available lay prices and corresponding stake amounts
• The current best prices on each side
• The depth of liquidity across multiple price levels

The order book is the core mechanism that enables peer-to-peer betting.

Structure of the Order Book

A typical order book has two sides:

Back Side (Buy Side)

• Displays odds available to back
• Shows how much money is available at each price
• Represents demand for backing a selection

Lay Side (Sell Side)

• Displays odds available to lay
• Shows how much money is available at each price
• Represents supply from users willing to oppose the selection

The best available back and lay prices form the spread.

Best Price and Spread

The best back price is the highest available price offered by backers.

The best lay price is the lowest available price offered by layers.

Example:

• Best back: 2.00
• Best lay: 2.02

Spread = 0.02

A smaller spread usually indicates higher liquidity.

Price Ladder and Levels

Prices in the order book are arranged in increments known as the price ladder.

Each level contains:

• The price (decimal odds)
• The available stake at that price

Example snapshot:

Lay Side
2.06 — €1,500
2.04 — €2,000
2.02 — €3,000

Back Side
2.00 — €4,000
1.98 — €2,500
1.96 — €1,200

This shows market depth across multiple levels.

Market Depth Explained

Market depth refers to the total available liquidity across several price levels in the order book.

Deep markets typically:

• Show large amounts of money at multiple prices
• Absorb large bets without major price shifts
• Provide greater price stability

Shallow markets:

• Have limited amounts at each level
• Experience faster price movement
• Show wider spreads

Market depth reflects structural stability.

How Orders Are Matched

The matching engine follows price-time priority:

1. Better price gets matched first
2. If prices are equal, earlier orders get matched first

Example:

• Two lay bets at 2.02
• The first placed order gets matched before the second

This ensures fairness and predictable execution.

Partial Matching in the Order Book

If you place a bet larger than available liquidity at the best price:

• The available portion is matched
• The remainder stays unmatched
• It may match at the next available price if allowed

Example:

You back €5,000 at 2.00.
Only €4,000 available at 2.00.

Result:

• €4,000 matched
• €1,000 remains unmatched

Order Cancellation and Price Movement

Unmatched orders can be cancelled at any time.

If large unmatched orders are removed:

• Market depth decreases
• Spread may widen
• Price may move more easily

The order book is dynamic and constantly changing.

Order Book vs Traditional Bookmaker Pricing

Traditional bookmakers:

• Set fixed odds
• Do not show underlying supply and demand
• Control price formation

Betting exchanges:

• Display full order book transparency
• Allow users to set prices
• Reflect real-time market consensus

The order book is central to exchange pricing.

Why Order Books Matter for Strategy

Understanding the order book helps with:

• Identifying support and resistance levels
• Timing entry and exit
• Avoiding slippage
• Executing trading strategies
• Managing large positions

Professional traders constantly monitor order book structure.

Common Mistakes and Misunderstandings

1. Assuming Displayed Liquidity Is Guaranteed

Large visible amounts can disappear if cancelled.

2. Ignoring Spread Size

Wide spreads increase execution cost.

3. Overestimating Market Depth

Liquidity at one level does not represent total market stability.

4. Confusing Order Book With Historical Volume

The order book shows current unmatched orders, not past matched volume.

FAQ

1. What is the order book used for?

It shows available prices and stake amounts for unmatched bets.

2. Does the order book update in real time?

Yes. It changes continuously as users place or cancel bets.

3. Can I see full market depth?

Most exchanges show multiple price levels, though display limits may apply.

4. Why does the spread widen?

Usually due to lower liquidity or sudden order cancellations.

5. Does order book size affect commission?

No. Commission applies to net winnings, not market depth.

6. Can large players move the order book?

Yes. Large orders can consume liquidity and shift prices.

7. Is the order book manipulated?

Price changes reflect real user activity, but large cancellations can create short-term volatility.

Summary

The order book is a real-time display of unmatched back and lay bets across different price levels.

• Shows supply and demand
• Determines spread
• Reflects market depth
• Drives price formation

Understanding the order book is essential for effective trading and advanced betting strategies on a betting exchange.