ABI surface
Standards
Nothing on-chain records that a contract is an ERC-20. What it has is a set of function selectors, and implementing the standard means exposing them. Detection here reads that surface rather than trusting a label, so a token that never declared itself still gets found — and one that claims the name without the methods does not.
ERC-20
Fungible tokensDetected from 8 of 10 transfer, approval and metadata selectors.ERC-721
Non-fungible tokensDetected from 7 of 10 ownership, approval and safe-transfer selectors.ERC-1155
Multi-tokenBatch transfer and balance selectors, plus ERC-165 support.ERC-4626
Tokenised vaultsDeposit, mint, withdraw and redeem accounting on top of ERC-20.ERC-165
Interface detectionA single selector, supportsInterface, that lets a contract answer for itself.