An order book is a real-time, continuously updated list of all open buy and sell orders for a particular trading pair on an exchange. It's one of the most fundamental tools in trading, giving you a transparent view of supply and demand at every price level. Learning to read an order book is a core skill for any trader working with perpetual futures or spot markets.
How an Order Book Is Structured
Every order book has two sides:
Bids (Buy Orders)
The bid side shows all open buy orders — traders willing to purchase the asset at specific prices. Bids are arranged from highest to lowest price. The highest bid is the best price a buyer is currently willing to pay.
Asks (Sell Orders)
The ask side (also called "offers") shows all open sell orders — traders willing to sell the asset at specific prices. Asks are arranged from lowest to highest price. The lowest ask is the best price a seller is currently willing to accept.
The Spread
The spread is the gap between the highest bid and the lowest ask. For example:
- Highest bid: $59,995
- Lowest ask: $60,005
- Spread: $10
A tight spread (small gap) indicates high liquidity and active trading. A wide spread suggests lower liquidity, meaning you'll likely pay more in slippage when executing trades.
Reading Order Book Depth
Beyond the best bid and ask, the order book shows the depth of orders at each price level — how much volume is sitting at every price point.
A typical order book display looks like this:
| Price (Ask) | Size | | ----------- | ------- | | $60,020 | 2.5 BTC | | $60,015 | 5.0 BTC | | $60,010 | 1.2 BTC | | $60,005 | 8.3 BTC | | Spread | | | $59,995 | 7.1 BTC | | $59,990 | 3.4 BTC | | $59,985 | 6.0 BTC | | $59,980 | 2.8 BTC | | Price (Bid) | Size |
The size at each level tells you how much volume needs to be traded to move the price to the next level. Large orders ("walls") at certain price levels can act as support or resistance — the price may struggle to move past a level where a large order sits.
What the Order Book Tells You
Experienced traders extract several types of information from the order book:
Liquidity Assessment
A deep order book with substantial volume at many price levels means the market is liquid. Your orders will fill with minimal slippage. A thin order book means even moderate-sized orders can move the price significantly.
Supply and Demand Imbalance
If the bid side has significantly more volume than the ask side, there's more buying pressure, which can push prices higher. The reverse suggests selling pressure. This imbalance isn't a guaranteed predictor, but it provides context for short-term price direction.
Support and Resistance Levels
Large clusters of buy orders at a specific price can act as support — many buyers are willing to step in at that level. Large clusters of sell orders can act as resistance — sellers are waiting to exit at that price. These levels often correspond to psychologically significant round numbers or known technical levels.
Spoofing and Fake Walls
Not all large orders are genuine. Some traders place large orders they intend to cancel before execution — a practice called spoofing. The goal is to create the illusion of support or resistance to manipulate other traders' behavior. If you see a large wall that suddenly disappears as price approaches it, that's a potential spoof.
Order Book vs. Depth Chart
Many trading interfaces offer a depth chart — a visual representation of the order book. It plots cumulative buy and sell volume on a chart, making it easy to see at a glance where liquidity is concentrated and how balanced the two sides are.
The depth chart is the same data as the order book, just presented graphically. Some traders prefer the raw numbers; others find the visual representation more intuitive.
Using the Order Book in Practice
For active traders, the order book informs several practical decisions:
- Order placement — placing limit orders at price levels with existing support (bids) or resistance (asks) increases the chances of execution at favorable prices
- Slippage estimation — before placing a large market order, checking the order book depth tells you how much price impact your order will have
- Entry and exit timing — watching for large orders being filled or pulled can signal imminent price moves
Order Books in Competitive Trading
On platforms like Legend, where traders compete in real-time duels and leaderboard rankings, reading the order book is a practical edge. Understanding where liquidity sits helps you enter and exit positions with better pricing, reduces slippage on your executions, and gives you insight into what other market participants are doing. In competitive environments where PnL margins between winning and losing can be razor-thin, the information advantage from order book literacy compounds over time.