Open any Spot Trading screen and the order book is usually the busiest, most intimidating part of it: two columns of shifting numbers, a wall of green and red, and a constantly updating price in the middle. It’s also one of the most useful tools on the page, once you know what you’re looking at. The order book and its companion depth chart show what buyers and sellers are actually offering right now, not what a chart pattern predicts or what a trader hopes will happen next. This guide walks through what each part of the order book means, what it can reasonably tell you, and where its usefulness ends.

What Is a Spot Order Book?

A Spot order book is a live list of every open buy and sell order for a trading pair, organized by price. Buy orders are called bids, and sell orders are called asks (sometimes “offers”). Each entry shows a price and a quantity: how much of the asset someone is willing to buy or sell, and at what price they’re willing to do it.

Order books typically also show cumulative volume: the total quantity available if you added up every order from the best price down (or up) to a given level. That running total is what eventually feeds into the depth chart, covered below.

Because the order book only shows orders that have been placed and not yet filled, it’s a snapshot of current interest, not a record of past trades or a projection of future ones.

Term	What It Shows	Why It Matters
Bid	The price and quantity a buyer is currently willing to pay	Sets the floor of current buying interest
Ask	The price and quantity a seller is currently willing to accept	Sets the ceiling of current selling interest
Spread	The gap between the best bid and best ask	A narrower spread generally points to a more liquid, actively traded market
Order-book depth	The total buy and sell quantity available at each price level	Gives a sense of how much volume it could take to move the price
Depth chart	A visual plot of cumulative bid and ask volume against price	Makes the shape of supply and demand easier to scan at a glance

How to Read Bids, Asks, and the Spread

Bids are usually listed from highest to lowest price, since the highest bid represents the most a buyer is currently willing to pay. Asks are listed from lowest to highest, since the lowest ask represents the least a seller is currently willing to accept.

The best bid and best ask sit closest together, and the gap between them is the spread. A narrow spread generally reflects a liquid market with active buyers and sellers close to agreement on price. A wider spread can indicate thinner trading interest or a market moving quickly enough that buyers and sellers haven’t converged.

It’s worth remembering that every order visible in the book can be changed or cancelled by the person who placed it at any time before it fills. Nothing displayed there is a commitment that survives beyond the moment it’s shown.

What Is a Depth Chart?

The depth chart is a visual version of the same order book data, plotting cumulative buy and sell volume against price instead of listing it row by row. On XT’s Spot Trading interface, order depth is displayed vertically: the green area below the current price represents accumulated buy orders (demand), and the red area above represents accumulated sell orders (supply).

The steepness and shape of each side can give a rough visual sense of how volume is distributed across price levels, but the chart is still just a picture of the same live, changeable order data described above.

What Order Book Depth Can Tell You

Read together, the order book and depth chart can help with a few practical things:

• Understanding current supply and demand. The relative size of the bid and ask sides at a moment in time reflects how much buying and selling interest currently exists.
• Assessing visible liquidity. More volume sitting closer to the current price generally means it takes more buying or selling pressure to move that price meaningfully.
• Estimating execution impact. If you’re placing a larger order, depth data can give a rough sense of how many price levels your order might need to work through to fill completely.
• Spotting where interest is concentrated. Clusters of orders at particular price levels show where more participants currently have orders resting.
• Adding context to recent trades. Looking at the book alongside recent trade activity gives a fuller picture of current conditions than either one alone.

None of this amounts to a guarantee. A large cluster of orders can look like a meaningful level and then be cancelled or reduced a moment later. Order book depth describes the market as it stands right now, not where it’s headed.

Order Book, Depth Chart, and Order Types

The order book isn’t just a display, it’s also where your own orders go once you submit them, and how they interact with it depends on the order type.

A Market Order is designed for immediate execution: it fills against whatever best-priced orders are currently sitting in the book, working through as many levels as necessary to complete the requested size. Because it prioritizes speed over price, a Market Order’s actual fill price can differ from the last traded price shown on screen, particularly for larger orders or in thinner markets.

A Limit Order, by contrast, is placed at a price you choose. If it doesn’t execute immediately because the market hasn’t reached your price, it joins the order book itself, adding to the visible depth other traders see, rather than being filled right away. This is generally what’s meant by a “maker” order: it rests in the book waiting for a match, rather than immediately taking liquidity that’s already there.

In fast-moving or lower-liquidity conditions, the gap between the price you see and the price you actually get can widen for both order types, which is exactly why understanding the book beforehand is useful.

Common Mistakes When Reading Market Depth

A few habits can lead to reading more into the order book than it actually shows:

• Treating a large visible order as a certain price barrier. Big bids or asks can be modified or pulled at any time; they aren’t a guarantee that price will stop there.
• Ignoring the spread. A wide spread changes the real cost of entering or exiting a position, even if the displayed price looks attractive.
• Forgetting that orders can be cancelled or changed. What you see now may not be there seconds later.
• Assuming a Market Order fills at a single, fixed price. Larger Market Orders often work through several price levels, not just the one you saw last.
• Looking at the book in isolation. Depth data means more when read alongside recent trade activity, volatility, and general liquidity conditions, not on its own.
• Treating book depth as a price forecast. Order book data reflects current interest, not a prediction of where the market goes next.

A Simple Spot Order Book Checklist

Before placing a Spot order, it can help to run through a short checklist:

• Confirm you’re on the correct trading pair.
• Identify the best bid, best ask, and the current spread.
• Review the visible depth near the current price on both sides.
• Decide between a Market Order (priority: speed) or a Limit Order (priority: price) based on what matters more for this trade.
• Double-check the order’s price, quantity, and total before submitting.
• After submitting, review your open and completed orders to confirm the order behaved as expected.

A Snapshot, Not a Forecast

An order book and its depth chart are a window into a market’s current buying and selling interest, and reading them well can improve your sense of liquidity and likely execution conditions. What they can’t do is guarantee that a visible level will hold, or tell you where the price is going next. Treat the data as a snapshot of the present, not a forecast of the future. For a closer look at how XT displays this information, see the official guide.

FAQs

What is an order book in crypto trading?

An order book is a live list of all open buy (bid) and sell (ask) orders for a trading pair, organized by price and quantity.

What is the difference between bids and asks?

Bids are open buy orders, typically listed from highest to lowest price. Asks are open sell orders, typically listed from lowest to highest price.

How do I read a crypto depth chart?

A depth chart plots cumulative buy and sell order volume against price. On XT, the green area below the current price shows accumulated demand, and the red area above shows accumulated supply.

What does market depth mean in Spot Trading?

Market depth refers to the total volume of buy and sell orders available at different price levels, which reflects how much order flow it would take to move the price at each level.

Can an order book predict crypto prices?

No. An order book and depth chart show current, changeable buy and sell interest at a specific moment. They are not a guaranteed forecast of future price movement.

About XT Exchange

Founded in 2018, XT Exchange is a leading global digital asset trading platform, serving over 12 million registered users across more than 200 countries and regions, with an ecosystem reach exceeding 40 million. XT Exchange supports 1,300+ tokens and 1,300+ trading pairs, offering a wide range of trading options, including spot, margin, and futures, alongside a secure RWA (Real World Assets) marketplace. Guided by the vision “Xplore Crypto, Trade with Trust,” the platform strives to provide a secure, trusted, and intuitive trading experience.

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