A token standard is the technical contract interface a token implements, defining how it behaves across wallets, exchanges, and protocols. The standard determines which venues can list the token, what compliance logic can live in the contract, and how composable it is with DeFi. Choose the wrong one and you narrow venues and widen spreads.
Standard selection is a decision, not a default. Specify classification, markets, and composability first, then justify the standard in writing before deployment.
How it works
A token standard is the published interface a smart contract implements, defining the functions, events, and data structures that wallets, exchanges, and other contracts expect. When a token implements ERC-20, every Ethereum wallet can display the balance, every DEX can create a pair, and every DeFi protocol can accept it as collateral. That composability is the economic value of a standard: it is infrastructure that exists before the token launches.
Design consequence
The three primary Ethereum standards each serve a different purpose. ERC-20 is the baseline fungible interface, universal, and deviating from it breaks DeFi compatibility without good reason. ERC-721 defines the non-fungible interface, where each token has a unique ID. ERC-3643, formerly T-REX, extends ERC-20 with an on-chain identity registry, transfer restriction hooks, and compliance modules, built for regulated securities that must enforce eligibility and jurisdiction rules at the contract level rather than through bypassable off-chain processes.
Common mistake
Picking a standard that fights the token's classification. A utility token on ERC-3643 signals expected transfer restrictions, which deters DEX listings and DeFi integrations because protocols cannot safely compose with a token that may refuse transfers without warning. A security token on bare ERC-20 leaves the issuer relying entirely on off-chain controls to prevent illegal transfers to ineligible investors, which is an enforcement liability, not a compliance posture.
How we approach it
We specify the classification first, then target markets, then composability requirements, and only then select the standard and document why each rejected alternative was unsuitable. On other chains the equivalents differ: Solana uses a Program Library token standard with similar fungibility logic, and Cosmos chains implement standards at the module layer. The principle holds everywhere: justify the choice in writing before the contract is deployed.
See Tokenomics Design Services for how this applies in practice.
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