When you deposit two tokens into a liquidity pool to provide liquidity, if the two tokens' relative price later changes, the value you eventually withdraw will be less than "doing nothing and just holding the two tokens" — that difference is impermanent loss. The more prices diverge, the bigger the loss; it only disappears if prices happen to return to where they were when you deposited, hence "impermanent."
Full Explanation+
01 · What is this?
Impermanent loss is a hidden loss unique to liquidity providers. When you deposit two tokens (say ETH and USDC) into a pool, the pool automatically rebalances their ratio as others keep trading. If ETH later surges, the mechanism shrinks your ETH in the pool and grows your USDC — so when you withdraw, the total value you get back is less than if "those ETH and USDC had sat untouched in your wallet." That shortfall versus just holding is impermanent loss. It's called "impermanent" because if prices ever return to where they started, the loss disappears.
02 · Why does it exist?
Why does impermanent loss happen? Its root is the pool's automatic pricing. The pool must keep some math relationship between the two tokens (most commonly the constant product x*y=k); when one token's market price rises, arbitrageurs come buy the "relatively cheaper" token from the pool and add the pricier one, until the pool's price catches up to the market. This continuously adjusts the amounts of your two tokens — the result is you always "have more of the appreciating token swapped away and keep more of the depreciating one." Compared with doing nothing and holding untouched, this automatic rebalancing leaves you earning less — the mathematical source of impermanent loss.
03 · How does it affect your decisions?
How does impermanent loss affect your decisions? It directly decides "whether providing liquidity is worth it." The reward for providing is fees (sometimes plus extra token incentives), but the cost is impermanent loss. The real profit/loss is "fee income minus impermanent loss." If your chosen pool's two tokens swing a lot and often surge or crash one-way, impermanent loss can easily eat or even exceed the fees you earn, leaving you worse than just holding. So when you see a pool touting "80% APR," don't rush — that number usually counts only fee rewards and doesn't subtract impermanent loss.
04 · What should you do?
How should you handle impermanent loss? First, grasp one principle: the more stable the two tokens' relative price, the smaller the impermanent loss. So beginners testing the waters should start with "two stablecoins" or highly correlated pairs, where it's tiny. Second, don't just look at advertised APR — roughly estimate yourself: under your expected price swings, about how big is the impermanent loss, and do the fees cover it. Third, treat it as "the cost of a directional bet" — if you're long-term bullish on both tokens anyway and don't mind short-term ratio changes, its psychological sting is smaller. Fourth, only commit what you can afford to lose, and factor in contract risk too.
Real-World Example+
Suppose you deposit $1,000 each of ETH and USDC into a pool when ETH is $2,000, so you put in 0.5 ETH plus 1,000 USDC, $2,000 total. Later ETH rises to $4,000. Had you done nothing and just held, that 0.5 ETH is now worth $2,000 plus 1,000 USDC, $3,000 total. But because they sat in the pool, arbitrageurs swapped your ETH away and added USDC, so when you withdraw, the combination the pool returns by ratio may be worth only about $2,828. That missing ~$172 is impermanent loss — your assets did rise, just less than "just holding."
Diagram
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Common Misconceptions+
✕ Misconception 1
× Misconception 1: It's called 'impermanent' loss, so just wait long enough and it disappears on its own. Wrong. It's called impermanent because the loss only disappears "if the price happens to return to your deposit level." If the price never comes back, the loss gets "locked in" as a real, permanent loss. Treating impermanent as "it'll always come back" is a dangerous misconception.
✕ Misconception 2
× Misconception 2: As long as a pool's APR is high enough, it must be worth it. Not necessarily. High APR is often just a fee or token-reward figure that doesn't subtract impermanent loss. The real return is what's left after "fee income minus impermanent loss"; in a pool with violent one-way price swings, even a high APR can be wiped out by impermanent loss.
The Missing Link+
Direct Impact
Providing liquidity lets you earn trading fees on two idle tokens — an important DeFi income source; but the cost is impermanent loss: whenever prices diverge from your deposit level, your outcome may be worse than just holding, and this cost is often hidden by high APR figures. Whether it's worth it depends on whether fee income can outweigh the impermanent loss.
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Impermanent Loss
無常損失
Impermanent loss = the shortfall vs just holding, caused by price moves after providing liquidity
It arises whenever the two tokens' relative price changes
The more prices diverge, the larger it gets (both directions)
If prices return to deposit levels at withdrawal, it goes to zero (hence impermanent)
Judge by whether fee income outweighs the impermanent loss
The Missing Link
Impermanent loss is the trap DeFi's high APR most easily hides: you think you're earning passive income, but never counted that once prices move, you may do worse than if you'd done nothing.