A depth chart turns the order book into two curves. Here is what each axis means, how to spot walls and thin books, and how to use it to guess the cost of a big order before you send it.
An order book is a list: every resting buy and sell order, stacked by price. A depth chart draws that list as a picture. Price runs along the bottom. Up the side is cumulative size: the total quantity you would have to trade through to get from the current price to that price.
In WatchCrypto the mid price sits in the centre as a vertical line. Bids (buyers) are the green curve on the left, rising as you move down in price. Asks (sellers) are the red curve on the right, rising as you move up. The top of the chart shows the mid price and the spread, the gap between the best bid and best ask, in price and as a percentage of mid.
Each point on a curve is a running total. Take a small illustrative book (the numbers are made up for the example, not live data):
The curve is a staircase: it is flat between order prices and steps up at each one, and the size of the step is the size of the order. That is why a big order is so easy to see. The 12-unit bid at 99.8 is a step taller than the two before it put together (8 units).
A steep curve means lots of size close to the mid price. It takes a lot of volume to push price through, so the market is deep. A shallow curve means thin liquidity, and a modest market order can move price a long way. Compare the same pair on two venues to see which one is easier to trade in size.
A wall is a tall vertical step: one large order, or a cluster at one price. While it stays, it can slow price down. But resting orders are free to cancel, which is why the order book guide treats walls with suspicion. Judge a wall by what happens when price gets close. If trades eat into it and it holds, it was real. If it vanishes as price approaches, it was never meant to fill.
Compare the two sides at the same distance from mid. If the bid curve is far higher than the ask curve at 0.5% away, there is more size under the market than above it, so selling meets more resistance than buying. Imbalance is a hint and not a forecast: size can be pulled in seconds, and the side with less size may simply be the side with the sharper traders.
A curve that is flat for a long stretch and then jumps means a gap with almost nothing resting, followed by a large order. Price can travel quickly across the gap, and the level at the far side is where the real interest is.
The depth chart answers a practical question: what will a market order of this size cost? Find your order size on the vertical axis, move across to the curve, and read the price below it. That is roughly where your last unit would fill. The distance from the mid price is your slippage in the worst case, before fees.
Use it before an order that is large for the market. A size that is fine on BTC can walk a long way on a small coin. The book changes quickly, so treat the answer as an estimate, and use a limit order if the estimate is uncomfortable.
Open it beside the chart on any chart page, as the Depth panel in the terminal, or with the Depth chip on a phone. The Scalper and Whale Watcher layouts in the terminal include it.
A depth chart plots the order book as cumulative size. Price runs along the bottom, and each curve shows the total size of bids (buy orders) or asks (sell orders) you would have to trade through to reach that price. Bids are drawn in green to the left of the mid price and asks in red to the right.
A steep curve means a lot of size sits at nearby prices, so it takes a lot of volume to push price through. A shallow curve means thin liquidity: a small order covers a lot of price distance.
A wall is a single large order, or a cluster at one price, that shows up as a vertical step in the curve. It can act as support or resistance while it stays, but resting orders can be cancelled for free, so a wall is a claim and not a fact until trades have eaten into it.
No. It shows the orders waiting at this moment. Orders are added, cancelled and filled constantly, so the picture can change within a second. Use it for the cost of trading now and the strength of nearby levels.
Yes. The depth chart is part of the free terminal and sits beside the chart on every market, with no account and no payment.