ERC-20 Token Standard
Ethereum token standard defining rules for fungible tokens — USDT, LINK, UNI.
ERC-20 (Ethereum Request for Comment 20) is a token standard defining a uniform set of rules for creating fungible tokens on the Ethereum blockchain.
What is a fungible token:
•Every unit is identical to all others
•1 USDT = 1 USDT (like 1 EUR = 1 EUR)
•Unlike NFT (ERC-721) where each is unique
ERC-20 interface (required functions):
•totalSupply() — total supply
•balanceOf(address) — address balance
•transfer(address, amount) — sending tokens
•approve(spender, amount) — approving spending
•transferFrom(from, to, amount) — transfer on behalf of
•allowance(owner, spender) — remaining approved amount
Well-known ERC-20 tokens:
•USDT, USDC, DAI — stablecoins
•UNI, AAVE, COMP — DeFi governance
•LINK, GRT — utility tokens
•SHIB, PEPE — meme coins
ERC-20 approve risk:
•When you approve a token for DEX, you give it spending rights
•Malicious smart contract can "steal" all approved tokens
•Revoke.cash — check and revoke unnecessary approvals
Other standards:
•ERC-721 — NFT (non-fungible)
•ERC-1155 — multi-token (gaming)
•ERC-4626 — vault standard (DeFi yield)