Crypto exchange order book: how it works and what it shows

An order book is one of the main tools for analyzing financial markets. It allows traders to monitor buy and sell orders, assess liquidity, and identify price levels where the balance between supply and demand may shift.

What is an order book?

An order book is an electronic record of active buy and sell orders for a particular asset. On cryptocurrency exchanges, a separate order book is maintained for each trading pair, such as BTC/USDT or ETH/USDT.

The order book displays the prices at which market participants are willing to trade, as well as the volumes of their orders.

All orders in the order book fall into two categories:

• Bids — buy orders indicating how much buyers are willing to pay for an asset.
• Asks — sell orders showing the prices at which sellers are willing to sell an asset.

On most trading platforms, buy orders are highlighted in green, while sell orders are displayed in red.

An order book provides insight not only into current prices but also into how supply and demand are distributed across different price levels. This helps traders assess market activity and the potential impact of large transactions on an asset's price.

How an order book works

An order book is constantly changing as new orders are submitted, existing orders are executed, and previously placed orders are canceled.

When a market participant places a limit order that cannot be executed immediately, it enters the order book. If another trader is willing to take the opposite side at a compatible price, the exchange's trading system matches the orders and executes the trade.

For example, one user places an order to sell 1 BTC for 70,000 USDT. Another participant is willing to buy the same amount of Bitcoin at that price. If the relevant conditions are met, the exchange automatically executes the transaction.

Once an order is fully executed, it disappears from the order book. If it is only partially filled, the unfilled portion remains in the book.

A key characteristic of an order book is that its information is continuously updated. On popular cryptocurrency exchanges, changes can occur many times per second as market participants constantly place, modify, and cancel orders.

Another important feature is that buyers and sellers form prices through direct interaction. When market buy orders progressively absorb available sell orders, trades begin executing at higher prices. The opposite happens during heavy selling: buy orders are filled at progressively lower price levels.

Key components of an order book

To analyze an order book effectively, you need to understand several key indicators.

Buy orders (Bids)

This section of the order book contains orders from participants looking to purchase cryptocurrency. Buy orders are sorted in descending order by price, with the highest bid appearing first.

For example, buyers may place the following orders:

• 69,990 USDT — 0.5 BTC;
• 69,980 USDT — 1.2 BTC;
• 69,950 USDT — 2 BTC.

The higher the bid price, the closer the order is to potential execution.

Sell orders (Asks)

The other section of the order book contains orders from asset holders willing to sell. These orders are sorted in the opposite direction, from the lowest asking price to the highest.

For example:

• 70,000 USDT — 0.8 BTC;
• 70,010 USDT — 1.5 BTC;
• 70,050 USDT — 3 BTC.

The most favorable offers for buyers are executed first, provided there is sufficient matching demand.

Price and volume

Each row in an order book typically contains two main values: the asset's price and the amount of cryptocurrency available for purchase or sale.

Some exchanges also display the cumulative order volume at a particular price level. This allows traders to estimate how much of an asset market participants are willing to buy or sell within a selected price range.

Spread

The spread is the difference between the highest bid price and the lowest ask price.

Suppose the highest bid for BTC is 69,990 USDT, while the lowest ask is 70,000 USDT. In this case, the spread is 10 USDT.

Generally, a narrow spread is characteristic of active markets with high liquidity. A significant gap between bid and ask prices may indicate insufficient trading activity or higher transaction costs.

However, a narrow spread alone does not guarantee high liquidity. The available order volume must also be considered.

When comparing assets, it helps to evaluate the spread not only in absolute terms but also as a percentage. For example, a 10 USDT spread when Bitcoin is trading at approximately 70,000 USDT represents about 0.014%. The same spread for an asset priced at 100 USDT would be much more significant, amounting to 10%.

Order matching mechanism

Orders are processed by a specialized exchange trading system known as the matching engine.

It determines which orders can be executed based on price, volume, and priority rules. Many centralized exchanges use a price-time priority system: orders with more favorable prices are processed first, and when prices are identical, earlier orders receive priority.

This means that an order may not be executed immediately, even when there is sufficient demand. For example, if a trader places a buy order at a price level where other buy orders already exist, the trader must wait for the earlier orders at that price level to be filled under the standard price-time priority system.

Execution speed depends not only on market activity but also on an order's position in the queue. As a result, two identical orders placed at the same price but at different times may be executed at different moments.

What is market depth?

Market depth indicates how much of an asset market participants are willing to buy or sell at various price levels.

The more liquidity is concentrated near the current market price, the easier it is to execute large transactions without significantly affecting the asset's price.

To visualize this information, cryptocurrency trading platforms use a depth chart.

It typically consists of two areas:

• The green area represents the cumulative volume of buy orders.
• The red area shows the cumulative volume of sell orders.

The horizontal axis represents the asset's price, while the vertical axis shows cumulative order volume.

A depth chart helps traders identify the price levels where the largest concentrations of orders are located and assess the market's ability to absorb substantial trading volumes.

For example, if a large number of sell orders are concentrated near the current price, a large market buy order may be executed without causing a sharp price increase. However, if sell orders are insufficient, a similar transaction could push the price significantly higher.

How to use an order book in trading

An order book helps traders assess current market conditions and identify potential price movement scenarios. Let's explore its main applications.

Identifying support and resistance levels

A large concentration of buy orders at a particular price level can sometimes form what is known as a buy wall. This may prevent the price from falling further because a significant volume of orders must be filled before the price can move lower.

Similarly, large sell orders can create a sell wall, potentially limiting an asset's price increase for a period.

However, these levels do not guarantee support or resistance. Market participants can cancel orders at any moment, so that visible liquidity may disappear quickly.

Assessing liquidity

An order book helps traders understand how easily a particular amount of cryptocurrency can be bought or sold.

If substantial volumes of opposing orders are concentrated near the current price, the likelihood of significant price movements during execution is generally lower.

In less liquid markets, even relatively small transactions can cause noticeable price fluctuations.

Analyzing potential slippage

Slippage occurs when the actual average execution price of a trade differs from the expected price.

Suppose a trader wants to buy 5 BTC, but only 1 BTC is available at the best ask price. The trader must buy the remaining amount at higher price levels if insufficient sell orders exist at the initial price.

As a result, the average purchase price will be higher than the first displayed ask price.

Analyzing market depth helps traders estimate potential slippage in advance, especially when executing large transactions.

Monitoring market activity

Changes in the order book may indicate increasing interest from buyers or sellers.

For example, an increase in buy order volume near the current price can sometimes suggest growing demand. However, remember that placing an order does not necessarily mean it will be executed.

Therefore, market sentiment should not be assessed solely on the ratio of bids to asks.

Types of orders

Cryptocurrency exchanges support different types of trading orders. Let's examine three of the most common.

1. Market order

A market order is used to buy or sell an asset at the best available prices at the time of execution.

Its main advantage is executing a transaction quickly, provided sufficient opposing liquidity is available.

However, the final execution price is not fixed in advance. If the order size exceeds the amount available at the best price, it may be filled across multiple price levels.

Market orders generally do not remain in the order book waiting for a suitable price. Instead, they are submitted for immediate execution.

2. Limit order

A limit order allows traders to specify the maximum price they are willing to pay when buying an asset or the minimum price they are willing to accept when selling it.

For example, if BTC is trading at 70,000 USDT, a trader may place a limit buy order at 69,500 USDT.

The trade will only be executed at the specified price or a more favorable one. If no suitable opposing orders are available, the order may remain in the order book until it is executed, canceled, or expires.

The main advantage of limit orders is price control. However, using them does not guarantee that a trade will take place.

The concepts of maker and taker are closely related to limit and market orders.

A maker adds liquidity to the order book by placing an order that is not executed immediately.

A taker, by contrast, removes available liquidity by executing against existing orders. Many cryptocurrency exchanges charge different trading fees for these two categories of participants.

3. Stop order

A stop order is a conditional order that is activated when a specified price level is reached.

These instruments are commonly used to limit losses or implement trading strategies based on particular market movements.

There are two common types:

• Stop-market order — a market order is created when the trigger condition is met.
• Stop-limit order — a limit order is activated when the specified price is reached.

Before the activation condition is met, a stop order generally does not appear in the public limit order book.

A stop-market order does not guarantee a specific execution price, while a stop-limit order may remain unfilled during sharp market movements.

Some trading platforms also support iceberg orders — large orders in which only a portion of the total volume is publicly displayed. As the visible portion is executed, the exchange may display another portion. This mechanism allows participants to execute substantial transactions without immediately revealing the full size of their orders.

Can order book data be trusted?

Despite the valuable information order books provide, their data does not always reflect market participants' genuine intentions.

Some traders place large orders to create the impression of significant buying or selling interest and then cancel those orders before execution.

This practice can be used to manipulate market expectations and is known as spoofing.*

* Spoofing is a form of market manipulation in which a trader places large buy or sell orders without genuinely intending to execute them. The goal is to create an artificial impression of strong demand or supply, influence other traders' expectations, and trigger price movements in a desired direction.

For example, a large buy wall may create the impression of strong support. However, if the order is canceled, the price may continue to decline.

Furthermore, an individual exchange's order book shows only orders available on that platform. It does not represent the entire cryptocurrency market's liquidity.

For this reason, traders should also consider actual executed trading volumes, price movements, and other market indicators when conducting their analysis.

Advantages and limitations of order books

Order books provide traders with valuable information, but they also have strengths and weaknesses.

Main advantages:

• Displaying current buy and sell orders.
• Helping traders assess available liquidity.
• Identifying potential support and resistance levels.
• Analyzing market depth and potential slippage.
• Monitoring changes in supply and demand in real time.

Main limitations:

• Orders can be modified or canceled at any time.
• Large order volumes do not guarantee that a price level will hold.
• Market manipulation through misleading orders is possible.
• Data is limited to a particular exchange or trading platform.
• An order book alone cannot reliably predict future price movements.

Overall, an order book is a valuable tool for assessing current liquidity and the balance between supply and demand. However, order book analysis becomes most informative when combined with trade history, trading volumes, and market price movements.