Two things get muddled here. Volume counts how much has changed hands; depth counts how much is waiting to trade right now, and depth is what protects your fill. A useful proxy is the gap between the best buy and best sell price in the <a href="/glossary/order-book/">order book</a>: wide spreads and sparse orders on either side of it signal that the market is thin.
The cost of thinness has a name. <a href="/glossary/slippage/">Slippage</a> is the difference between the price you expected and the price you got, and it grows with your order size relative to available depth. It is why a token can look perfectly tradable in small amounts and become expensive to exit at any meaningful size, and why exchanges let you set a maximum tolerance before a trade goes through.
On decentralised exchanges the mechanics differ but the principle survives. Instead of matching orders, trades run against a <a href="/glossary/liquidity-pool/">liquidity pool</a> funded by depositors, and a formula sets the price from the ratio of assets in the pool. A larger pool absorbs a given trade with less price impact. A small one moves sharply, which is exactly the same problem wearing different clothes.
The caveat that matters most is that liquidity is not a fixed property. It is deepest when nobody needs it and thinnest during the stress when everyone does, because market makers widen or withdraw as risk rises. Reported volume can also be manufactured by accounts trading with themselves, so busy-looking figures are not proof that you could sell.
DeFi Basics and Risks
Key takeaways
- Depth on the book, not headline volume, determines what your order actually costs to fill.
- Liquidity tends to disappear precisely when markets are stressed and exits are most wanted.
- The same asset can be liquid at small size and effectively illiquid at large size, so scale the question to your own order.
Liquidity — frequently asked questions
How can I tell if a market is liquid before trading?
Look at the order book rather than the volume figure: check the spread between best bid and best ask, and how much size is stacked within a small distance of the current price. On a decentralised exchange, check the size of the pool relative to your intended trade. Simulating the trade in the interface will usually show the estimated price impact directly.
Does high trading volume always mean good liquidity?
No. Volume is a record of past activity and can be inflated by wash trading or by a single burst of turnover, while liquidity is about the orders standing there now. A market can post large daily volume and still have a thin book between bursts. Depth at the moment you want to trade is what determines your outcome.
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