A token standard is a publicly agreed smart contract interface that defines which functions and events a token must implement, so that wallets, exchanges and other contracts can hold, transfer and display any compliant token without custom code. On Ethereum and compatible networks, the best-known examples are ERC-20 for fungible tokens, ERC-721 for non-fungible tokens and ERC-1155 for mixed collections.
In the field of Tokenization & NFTs, token standards are the reason a newly issued token works in thousands of applications on its first day. They specify the shape of the token, not its value or rights: a standard says how to ask for a balance or move a token, while the legal meaning of owning that token is defined elsewhere.
What a token standard specifies
A token standard is a contract-level agreement. It lists function signatures with their exact names, parameter types and return values, the events that must be emitted, and the expected behavior in edge cases such as transfers of zero or transfers to unknown contracts. Because external software calls these functions by their binary selectors, even a small deviation can break compatibility.
On Ethereum, standards are proposed as Ethereum Improvement Proposals and, when they concern applications rather than the protocol, labeled ERC, for Ethereum Request for Comments. A proposal moves through draft, review and final status. Final status means the interface is frozen; improvements then arrive as new, separate standards or optional extensions.
Most standards define a minimal core plus optional extensions. ERC-20, for example, requires functions such as transfer, approve, transferFrom and balanceOf, while name, symbol and decimals are optional metadata. Extensions add features such as permit signatures, royalty information or enumeration of all tokens.
The main token standards compared
Each widely used standard answers a different question about fungibility and batching. The table summarizes the core differences.
| Standard | Token type | Key feature | Typical use |
|---|---|---|---|
| ERC-20 | Fungible | Balances and allowances per address | Currencies, stablecoins, governance tokens |
| ERC-721 | Non-fungible | Unique token ID with one owner | NFT art, domain names, unique records |
| ERC-1155 | Fungible and non-fungible | Many token types in one contract, batch transfers | Game items, editions, tickets |
| ERC-4626 | Fungible vault share | Standard deposit and withdrawal accounting | Yield vaults and tokenized funds |
| ERC-3643 | Permissioned fungible | Transfers limited to verified identities | Security tokens and regulated assets |
| ERC-5192 | Non-transferable | Minimal lock signal on ERC-721 | Soulbound tokens and credentials |
Other blockchains have their own standards built on different account models. Solana uses a shared token program in which tokens are accounts rather than separate contracts, and many networks adopt ERC-like interfaces directly because they run the EVM.
How a standard enables interoperability
The value of a token standard comes from network effects on the integration side. A wallet that supports ERC-20 automatically shows balances for every compliant token; a decentralized exchange can list any of them; a lending market can accept them as collateral after a risk review rather than a code change.
Standards also define safe interaction patterns. ERC-721 and ERC-1155 include safe transfer functions that check whether a receiving contract can handle the token, which prevents tokens from being locked forever in contracts that do not expect them. ERC-20 lacks this check, and tokens sent by mistake to a contract address are a long-standing source of permanent losses.
| Integrator | What it uses | Benefit |
|---|---|---|
| Wallet | Balance and metadata functions | Displays tokens without manual setup |
| Decentralized exchange | Approve and transferFrom | Lists any compliant token |
| NFT marketplace | Ownership, approval and metadata URI | Trades any collection |
| Indexer and explorer | Standard transfer events | Tracks history across all tokens |
Choosing a token standard
The choice follows from what the token represents and who may hold it. Picking the wrong standard is costly, because deployed contracts are hard to migrate and holders would need to swap into a new token.
| Requirement | Recommended standard | Reason |
|---|---|---|
| Interchangeable units such as a currency | ERC-20 | Widest support in wallets and DeFi |
| One-of-a-kind items with individual history | ERC-721 | Clear unique ownership per token ID |
| Many item types and editions in one project | ERC-1155 | Lower gas through batch operations |
| Shares in a pool that earns yield | ERC-4626 | Predictable deposit and redemption math |
| Regulated securities with transfer rules | Permissioned standard such as ERC-3643 | Enforces eligibility on every transfer |
For real-world asset tokenization, the technical standard is only one part of the design. The legal wrapper, custody of the underlying asset and the issuer’s obligations decide whether a token is a security token, a utility token or a simple record. A token standard cannot create those rights by itself.
Limitations and common pitfalls
- Compliance is not security. A token can follow the interface exactly and still contain a malicious mint function or hidden fees.
- Non-standard behavior breaks integrations. Tokens that charge transfer fees or rebase balances often fail in DeFi protocols that assume standard behavior.
- Unlimited approvals are risky. The allowance model of ERC-20 lets users grant spending rights that attackers exploit in approval phishing.
- Metadata often lives off-chain. An NFT’s image and attributes may sit on a server that can disappear, even though the token itself persists.
- Royalties are not enforced by the standard. ERC-2981 only reports a royalty amount; marketplaces decide whether to pay it.
The simple explanation
A token standard is like the agreed shape of an electrical plug. Because every appliance in a country uses the same plug, you can connect any device to any socket without an adapter.
In the same way, when a new digital token follows a known standard, every compatible wallet, exchange and marketplace can work with it immediately. The standard says how the token connects, not what it is worth or what it gives you.
How it is used in practice
A game studio plans to sell digital items: 50,000 copies each of ten common potions and 500 unique legendary swords. Writing one ERC-20 contract per potion and an ERC-721 contract for the swords would mean eleven contracts and separate transfers for every item.
Instead, the studio deploys a single ERC-1155 contract in which each potion is a fungible token ID with a large supply and each sword is a token ID with a supply of one. A player who buys a bundle of three potions and one sword receives them in one batch transfer, which costs noticeably less gas. Because the contract follows the standard, the items appear automatically in common wallets and can be listed on existing NFT marketplaces without any custom integration by those platforms.