ERC-20: Token Standard
ERC-20 is the most widely deployed standard in the Ethereum ecosystem. Every DeFi integration, exchange, and wallet interacts with ERC-20 tokens constantly.
What It Defines
Defines the standard interface for fungible tokens on EVM chains: totalSupply, balanceOf, transfer, transferFrom, approve, allowance events. Every fungible token (USDC, WETH, DAI, etc.) implements this interface.
Canonical (Normative)
Convenient (Practical)
The Ethereum community's open process for proposing changes to the protocol. EIPs cover core protocol changes; ERCs (Ethereum Request for Comments) cover application-layer standards like token interfaces.
Related Specs
NFTs, digital ownership, gaming assets, and on-chain certificates all use ERC-721. The standard that launched the NFT market.
More gas-efficient than deploying separate ERC-20 + ERC-721 contracts. Standard for gaming, semi-fungible assets, and multi-edition NFTs.
All Ethereum JSON-RPC APIs (Infura, Alchemy, local nodes, MetaMask) use JSON-RPC 2.0. You need to know the protocol to interact with EVM chains.
EIP-2612 is how DEXes, lending protocols, and meta-tx relayers achieve gasless approvals. If you're integrating ERC-20s into any UX where the user shouldn't need ETH first, permit() is the canonical solution. DAI, USDC, and most modern stablecoins implement it.
EIP-3009 is the gasless transfer primitive USDC uses on Ethereum and Base. It's the on-chain mechanism behind the x402 "exact" scheme: the buyer signs an authorization, the seller (or facilitator) submits it on-chain to settle. If you're building anything that spends USDC on behalf of a user without them paying gas, this is the spec.