ERC-20

The token standard on Ethereum that defines a common interface for fungible tokens: transfer, approve, allowance, and balanceOf functions. Most DeFi tokens, stablecoins, and governance tokens are ERC-20s. The standard enables composability: any ERC-20 can interact with any protocol that accepts the interface, without custom integration per token. Tokens that break the standard silently (such as tokens that automatically deduct a percentage fee on each transfer) cause unexpected behavior in protocols that do not account for it.