When you open a crypto trading platform, you may see a list of buy and sell orders next to the price chart. This list is called an order book.
It shows the prices at which traders want to buy or sell an asset. As a result, the order book helps you understand the current demand and supply in a market.
Before placing a trade, it is useful to understand how this list works and what the numbers mean.
What is an Order Book?
An order book is a live list of buy and sell orders for a particular trading pair.
For example, suppose you are looking at the BTC/USDT trading pair.
The order book may show:
- Traders who want to buy BTC
- Traders who want to sell BTC
- The price of each order
- The amount traders want to buy or sell
Depending on the platform, the buy side usually appears below or beside the sell side.
Meanwhile, traders can place, change, or cancel orders. Therefore, the order book can change quickly.
In simple terms, an order book gives you a snapshot of buying and selling interest in a market.
What are Bids?
A bid is a buy order.
It shows the price a trader is willing to pay for an asset.
For example, imagine the BTC/USDT market has these bids:
| Bid Price | Amount |
|---|---|
| 99,900 USDT | 0.50 BTC |
| 99,850 USDT | 0.80 BTC |
| 99,800 USDT | 1.20 BTC |
Here, traders have placed bids at different prices.
The highest bid is the highest price a buyer currently offers.
If a seller accepts that price, the two orders can match and a trade can take place.
What are Asks?
An ask is a sell order.
It shows the price at which a trader is willing to sell an asset.
For example, imagine the order book shows:
| Ask Price | Amount |
|---|---|
| 100,000 USDT | 0.40 BTC |
| 100,050 USDT | 0.70 BTC |
| 100,100 USDT | 1.00 BTC |
In this case, the lowest ask is the lowest price a seller currently offers.
When a buyer accepts an available ask, the order can be matched and a trade can occur.
Therefore, bids represent buying interest, while asks represent selling interest.
What is the Spread?
The spread is the difference between the highest bid and the lowest ask.
For example:
- Highest bid: 99,900 USDT
- Lowest ask: 100,000 USDT
- Spread: 100 USDT
So, the spread is:
100,000 − 99,900 = 100 USDT
Generally, a smaller spread means the buy and sell prices are closer together.
However, spread size can change as market conditions and trading activity change.
For this reason, the spread you see at one moment may be different a few seconds later.
What is Market Depth?
Market depth refers to the number and size of buy and sell orders available at different prices.
For instance, imagine an order book with many large orders close to the current market price.
In that situation, this order list has more visible depth around those price levels.
On the other hand, an order book with fewer available orders may have less visible depth.
Market depth can help traders understand how much buying and selling interest exists at different prices.
However, keep in mind that an order can be cancelled before it is executed. Therefore, this order list does not guarantee that every displayed order will remain available.
How does an Order Book work?
The process is fairly simple.
First, a trader places a buy or sell order.
Next, the order enters the order book if it cannot be matched immediately.
Then, the exchange looks for a compatible order on the other side.
For example, a buyer may place an order to buy BTC at 100,000 USDT.
If a seller is willing to sell BTC at that price, the orders can match.
Once the trade happens, the matched orders are removed or reduced from the order book.
As a result,this order list keeps changing as traders place, modify, cancel, and execute orders.
Order Book vs Price Chart
An order book and a price chart show different information.
| Order Book | Price Chart |
|---|---|
| Shows current buy and sell orders | Shows price movement over time |
| Shows bids and asks | Shows historical and current price data |
| Helps view available market depth | Helps study price trends and patterns |
| Can change very quickly | Changes as new price data appears |
Therefore, the two tools can provide different views of the same market.
A price chart helps you see how the market has moved over time. In contrast, this order list shows available buy and sell interest at that moment.
Together, they can help you understand different parts of market activity.
Why is an Order Book important?
An order book can help traders understand the current structure of a market.
For example, it can show whether there are many visible orders near a particular price.
It can also help traders see the current spread between buyers and sellers.
Furthermore, market depth can provide information about the amount of visible liquidity around different price levels.
Even so, you should not treat this order list as a prediction tool.
Orders can change or disappear quickly. In addition, the order book only shows available orders at that moment.
Therefore, it is better to view this order list as a source of current market information rather than a guarantee of what will happen next.
What should beginners look for?
When reading an order book, start with four basic things:
1. Highest Bid
First, check the highest price currently offered by buyers.
2. Lowest Ask
Next, check the lowest price currently offered by sellers.
3. Spread
Then, compare the highest bid with the lowest ask.
4. Market Depth
Finally, look at the size and number of orders around different price levels.
Together, these four points can help beginners understand the basic structure of an order book.
A Simple Order Book Example
Suppose the BTC/USDT order book looks like this:
Sell Orders
| Price | BTC |
|---|---|
| 100,200 | 0.5 |
| 100,100 | 0.8 |
| 100,000 | 1.0 |
Buy Orders
| Price | BTC |
|---|---|
| 99,900 | 0.7 |
| 99,800 | 1.0 |
| 99,700 | 1.5 |
From this example:
- The lowest ask is 100,000 USDT.
- The highest bid is 99,900 USDT.
- The spread is 100 USDT.
- The displayed orders show visible market depth at these prices.
If a buyer places an order that matches an available sell order, a trade can occur.
As more orders are placed or executed, these numbers can change.
Common Beginner Mistakes
Confusing the Bid With the Ask
The easiest way to remember is:
Bid = Buy
Ask = Sell
Assuming Large Orders Cannot Move
However, large orders can be cancelled or changed before execution.
Therefore, seeing a large order does not mean that the order will definitely result in a trade.
Treating the Order Book as a Prediction
An order book shows current orders. It does not, however, guarantee future price movement.
Instead, use it to understand the current buying and selling activity.
Ignoring the Spread
Finally, remember that the difference between the highest bid and lowest ask can matter when placing trades.
FAQs
What is an order book in crypto?
It is a live list of buy and sell orders for a specific trading pair.
What is a bid?
A bid is an order to buy an asset at a specified price.
What is an ask?
An ask is an order to sell an asset at a specified price.
What is the spread in an order book?
The spread is the difference between the highest bid and the lowest ask.
What does market depth mean?
Market depth refers to the amount of buy and sell orders available at different price levels.
Can an order disappear from the order book?
Yes. For example, a trader can cancel or change an order before it is executed.
Does an order book predict the price?
No. It shows current available orders and market activity. However, it does not guarantee future price movements.
Disclaimer
This lesson is for educational purposes only. It does not provide financial, investment, trading, or legal advice.
Crypto markets can be volatile, and trading involves risk. Therefore, always understand how an order works before placing a trade.