What Is Oracle?
An oracle is a service that provides external, real-world data to smart contracts running on a blockchain. Smart contracts are deterministic and can only access data within the blockchain — they can't natively fetch price feeds, weather data, or sports scores. Oracles bridge this gap, feeding off-chain information on-chain.
How Oracle Works
The most critical oracle use case is price feeds for DeFi protocols. Lending protocols use oracles to determine collateral values and trigger liquidations. DEXs use them for limit orders and stop-losses. Derivatives protocols use them for settlement. Chainlink is the dominant oracle network, using decentralized node operators who aggregate data from multiple sources to provide manipulation-resistant price feeds.
Why It Matters for Traders
Oracle manipulation is one of the most common DeFi attack vectors. If an attacker can temporarily distort an oracle's price feed (through flash loans, low-liquidity manipulation, or targeting a weak oracle source), they can create artificial liquidations or borrow far more than their collateral is worth. When evaluating DeFi protocols, the quality and decentralization of their oracle solution is a critical security factor.