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A token standard is an agreed interface a token contract implements: which functions it exposes, which events it emits, and what those events mean. Standards are what let a wallet display a token it has never seen before, and what let an indexer interpret a transfer without reading the contract’s source. They are also the main reason blockchain data is harder than it looks. There is no single global token standard — each ecosystem has its own, several ecosystems have more than one, and plenty of real tokens follow none of them exactly.

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Ethereum and EVM chains

ERC-20 and ERC-721 are the same standard family, and this causes real confusion: both emit an event called Transfer, with a third parameter that is an amount for ERC-20 and a token ID for ERC-721. Deciding which is which requires knowing the contract’s type, which is metadata the event itself does not carry.
Standards are conventions, not enforcement. A contract can call itself ERC-20 and behave differently. Fee-on-transfer tokens move less than the transferred amount; rebasing tokens change every holder’s balance with no Transfer event at all; some tokens move value through internal calls and emit no event. Any dataset built purely from Transfer events will be wrong for these tokens — which is why Allium reconciles balances against onchain state rather than deriving them from events alone.

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Solana

Solana does not put token logic in per-token contracts. A single Token Program owns all token accounts, and each token is a mint account with its own supply and decimals. The practical consequence: on Solana a wallet’s holdings are spread across associated token accounts, so “the balance of this address” requires resolving account ownership rather than reading a single mapping. NFTs are just mints with a supply of one, so nothing in the token model itself tells you an asset is an NFT.

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Other ecosystems

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Why Allium normalizes

Every one of those models answers “who holds what” differently. Reading them yourself means writing a distinct extraction path per ecosystem, then keeping each one correct as programs and standards change. Allium’s job is to collapse that into one shape:
When a number disagrees with a block explorer, check the token standard before checking the pipeline. Fee-on-transfer, rebasing, and compressed assets account for most apparent discrepancies. Data caveats lists the known cases.

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