ERC-20 is the Ethereum token standard: a small interface of six functions and two events that any fungible token contract implements. Because every token exposes the same methods, any wallet, exchange or protocol can hold and move a token it has never seen before.
ERC-20
ERC-20 is a nine-item interface that became the economic substrate of an entire market. totalSupply, balanceOf, transfer, transferFrom, approve, allowance and two events — that is the whole contract, and it is enough that a wallet written years before a token existed can hold it correctly.
- A minimal interface - Six functions and two events, small enough that everyone implements it identically.
- Permissionless interoperability - No registry, no onboarding, no negotiation — conformance is the whole integration.
- Approve and transferFrom - The delegation pattern that lets a contract spend on a user’s behalf, and the source of most allowance-related risk.
- A template for the rest - ERC-721 and ERC-1155 followed the same shape for non-fungible and mixed assets.
ERC-20 is the strongest counterexample in the catalog to the idea that standards need a mandate. Nobody was compelled to adopt it. It won because conformance was cheaper than coordination. The State of Blockchain & Crypto APIs shows what that did and did not achieve: superb interoperability at the protocol layer, and a service layer where each vendor still hand-rolls authentication, rate limits, errors and scopes.
Referenced in API Evangelist papers
This standard shows up in my published research. These reports read the machine-readable evidence provider by provider — and put this standard in the context of a real sector.
The State of Blockchain & Crypto APIs
Voluntary standardisation that actually worked — a nine-item interface that made tokens portable, in a market whose service layer is still hand-rolled vendor by vendor.
