A DeFi loan begins with more collateral value than debt, but crypto prices can move quickly. If the collateral falls far enough, the protocol cannot wait for a human conversation or a monthly payment. Its smart contracts enforce a liquidation rule.
Each market defines a threshold that determines how much borrowing a particular asset can support. Interfaces may summarise the buffer as a health factor. A comfortable value means the collateral can absorb some decline; a value near the limit means even a small price move may make the position eligible for liquidation.
When the threshold is crossed, an independent liquidator can repay part of the borrower’s debt and receive some collateral, usually with a bonus. That reward motivates bots to act quickly. The protocol reduces risky debt, lenders remain better protected, and the borrower loses collateral plus a penalty.
Consider ether collateral worth $1,500 against an $800 loan. If ether falls and the permitted borrowing limit drops below the debt, liquidation can begin. Adding collateral or repaying part of the loan before that point restores the safety margin. Watching only the original deposit price is not enough because the relevant values update continuously.
Liquidation depends heavily on price oracles. A delayed or manipulated price can liquidate healthy users or leave the protocol with bad debt. Network congestion also matters: when many positions fail together, gas costs rise and liquidators may struggle to process them quickly.
Borrowers can reduce risk by using less leverage, choosing strong collateral, maintaining a wide buffer, monitoring alerts, and understanding the exact threshold and penalty. There is no universal safe ratio because volatility, oracle design, and protocol rules differ.
Liquidations show that attractive borrowing and lending rates come from a system of incentives and risk controls. Tomorrow we will ask the broader question behind every advertised return: where does crypto yield actually come from?