The blockchain world is full of tokens, cryptocurrencies, stablecoins, NFTs, governance tokens, and countless others, and they work together with a remarkable degree of consistency. A token can be held in many different wallets, traded on many different exchanges, and used across many different applications, all without each one needing custom integration for each token. How? The answer is token standards: common sets of rules that define how tokens behave, so that any token following a standard works consistently with the wallets, exchanges, and applications that support that standard. The most famous are ERC-20, the standard for fungible tokens, and ERC-721, the standard for non-fungible tokens (NFTs). Token standards are a quietly essential piece of blockchain infrastructure, because they're what make the token ecosystem interoperable, letting tokens and the tools that handle them work together seamlessly. Understanding what token standards are, what ERC-20 and ERC-721 do, and why standards matter is valuable for anyone working with or building tokens.
This guide explains what token standards are, ERC-20 for fungible tokens, ERC-721 for NFTs, why standards enable interoperability, and why they matter.
What Token Standards Actually Are
A token standard is a common set of rules and specifications that defines how a token behaves, what functions it has, and how it can be interacted with, so that tokens following the standard work consistently with the broader ecosystem of wallets, exchanges, and applications. Rather than every token being built differently and needing custom handling, token standards provide agreed templates that tokens follow, ensuring they behave predictably and work with any tool that supports the standard.
The essential idea is that token standards provide consistency and interoperability through common rules. When a token follows a standard, any wallet, exchange, or application that supports that standard knows how to handle it, because the standard defines how the token behaves, without needing custom integration for that specific token. This is what lets the vast ecosystem of tokens and the tools that handle them work together: they all speak the common language of the standards. Token standards are typically defined for particular blockchain platforms (the "ERC" standards, for example, are Ethereum standards), and they're implemented through the smart contracts that create and govern tokens, as explored in the token economics covered in this guide to tokenomics. Token standards, in short, are the common rules that make tokens interoperable and consistent, a foundational piece of infrastructure that lets the token ecosystem function as a connected whole rather than a chaos of incompatible tokens.
ERC-20: The Standard for Fungible Tokens
The most widely-known token standard is ERC-20, the standard for fungible tokens on Ethereum. Understanding it means understanding what "fungible" means: fungible tokens are interchangeable, each unit is identical to and interchangeable with every other unit, like currency, where one dollar is the same as any other dollar. Most cryptocurrencies, stablecoins, and many other tokens are fungible, and ERC-20 is the standard they typically follow.
ERC-20 defines a common set of functions and rules that a fungible token implements, such as how tokens are transferred, how balances are checked, and how the token's supply works. Because ERC-20 provides this common template, any ERC-20 token works consistently with the wallets, exchanges, and applications that support ERC-20, which is essentially the entire Ethereum ecosystem. This is enormously powerful: it means a new fungible token following ERC-20 immediately works with the vast existing ecosystem of ERC-20-compatible tools, without needing custom integration. ERC-20's role in enabling the explosion of tokens is hard to overstate, by providing a standard that fungible tokens follow, it made the token ecosystem interoperable and let countless tokens work seamlessly with existing infrastructure. ERC-20 is, in short, the standard that makes fungible tokens interoperable, and it's one of the most important and widely-used standards in the blockchain world, underpinning much of the activity explored in this guide to decentralized finance.
ERC-721: The Standard for Non-Fungible Tokens (NFTs)
The other famous token standard is ERC-721, the standard for non-fungible tokens (NFTs) on Ethereum. "Non-fungible" is the opposite of fungible: non-fungible tokens are unique, each one is distinct and not interchangeable with others, unlike currency. This makes them suited to representing unique items, a specific piece of digital art, a particular collectible, a unique asset, where each token is one-of-a-kind rather than interchangeable.
ERC-721 defines the common rules for these unique tokens, how ownership of a unique token is tracked and transferred, and how each token is distinguished as unique. By providing a standard for non-fungible tokens, ERC-721 did for NFTs what ERC-20 did for fungible tokens: it made them interoperable, so NFTs following ERC-721 work consistently with the wallets, marketplaces, and applications that support the standard. This standardization is what enabled the NFT ecosystem, by providing a common standard for unique tokens, ERC-721 let NFTs be created, owned, traded, and used across a whole ecosystem of compatible tools, which is central to the unique-asset use cases explored in this guide to NFT solutions. ERC-721 is, in short, the standard that makes non-fungible tokens interoperable, enabling the NFT ecosystem much as ERC-20 enabled the fungible token ecosystem. Together, ERC-20 (fungible) and ERC-721 (non-fungible) are the two most important token standards, covering the two fundamental types of tokens.
Why Standards Enable Interoperability
The deeper point behind token standards is interoperability, and it's worth understanding why this matters so much. Interoperability means that tokens and the tools that handle them (wallets, exchanges, marketplaces, applications) work together seamlessly, and token standards are what make this possible. Without standards, every token would be built differently, and every wallet, exchange, or application would need custom integration for every token, an impossible, fragmented mess that would make the token ecosystem unworkable. With standards, any token following a standard automatically works with any tool supporting that standard, so tokens and tools interoperate without custom work.
This is why token standards are such essential, if often invisible, infrastructure: they're what let the vast token ecosystem function as a connected, interoperable whole. A new token following a standard instantly plugs into the existing ecosystem of compatible wallets, exchanges, and applications; a wallet supporting a standard automatically handles every token following it. This interoperability, enabled by common standards, is what made the explosion of tokens and the rich ecosystem of tools around them possible, since it let everything work together rather than requiring custom integration for every combination. Token standards, in short, matter because they enable the interoperability that makes the token ecosystem work, which is a foundational, enabling role even though standards themselves are rarely in the spotlight. They're the common language that lets the whole ecosystem connect, and the tokens held in the wallets across the ecosystem depend on them.
Why Token Standards Matter
Token standards matter because they're the foundation that makes the token ecosystem interoperable and functional, and understanding them clarifies how tokens actually work together. For anyone creating a token, following the appropriate standard (ERC-20 for a fungible token, ERC-721 for an NFT, or the relevant standard on another platform) is what makes the token work with the existing ecosystem, so understanding standards is essential to creating usable tokens. For anyone building applications that work with tokens, standards are what let the application handle tokens consistently. And for anyone trying to understand the token ecosystem, standards explain how the vast variety of tokens works together seamlessly, through the common rules they follow. There are also other token standards beyond ERC-20 and ERC-721 (for different purposes and on different platforms), but these two are the most important to understand, representing the fungible and non-fungible types. For businesses creating or working with tokens, understanding and correctly following token standards is essential to building tokens that function in the ecosystem, and it's the kind of foundational knowledge that experienced blockchain development brings, along with the honest advisory about whether and how tokens genuinely fit a use case. Token standards, in short, matter because they're what make tokens work, interoperably and consistently, across the blockchain ecosystem.
FAQs
Q1. What is a token standard?
A token standard is a common set of rules and specifications defining how a token behaves, what functions it has, and how it can be interacted with, so tokens following the standard work consistently with the ecosystem of wallets, exchanges, and applications. Rather than every token being built differently and needing custom handling, standards provide agreed templates that ensure tokens behave predictably and work with any tool supporting the standard, enabling interoperability.
Q2. What is ERC-20?
ERC-20 is the standard for fungible tokens on Ethereum. Fungible tokens are interchangeable, each unit identical to every other, like currency, and most cryptocurrencies and stablecoins are fungible. ERC-20 defines common functions and rules (how tokens are transferred, how balances work) so any ERC-20 token works consistently with the vast ecosystem of ERC-20-compatible wallets, exchanges, and applications, without custom integration. It's one of the most important and widely-used token standards.
Q3. What is ERC-721?
ERC-721 is the standard for non-fungible tokens (NFTs) on Ethereum. Non-fungible tokens are unique, each distinct and not interchangeable, suited to representing unique items like digital art or collectibles. ERC-721 defines common rules for how ownership of a unique token is tracked and transferred, making NFTs interoperable so they work with compatible wallets, marketplaces, and applications. It enabled the NFT ecosystem much as ERC-20 enabled the fungible token ecosystem.
Q4. What's the difference between fungible and non-fungible tokens?
Fungible tokens are interchangeable, each unit identical to and interchangeable with every other, like currency where one dollar equals any other, and most cryptocurrencies and stablecoins are fungible (typically following ERC-20). Non-fungible tokens are unique, each one distinct and not interchangeable, suited to representing unique items like art or collectibles (typically following ERC-721). The two represent the fundamental types of tokens, covered by the two most important token standards.
Q5. Why do token standards matter?
Because they enable interoperability, the ability of tokens and the tools that handle them (wallets, exchanges, applications) to work together seamlessly. Without standards, every token would need custom integration with every tool, a fragmented mess; with standards, any token following a standard automatically works with any tool supporting it. This interoperability made the explosion of tokens and the rich ecosystem around them possible, making standards essential, if often invisible, blockchain infrastructure.
Final Thoughts
Token standards are the quietly essential infrastructure that makes the blockchain token ecosystem work. By providing common rules that define how tokens behave, standards let any token that follows them work seamlessly with the wallets, exchanges, and applications that support them, enabling the interoperability that otherwise would require impossible custom integration for every token and tool. ERC-20, the standard for fungible (interchangeable) tokens, and ERC-721, the standard for non-fungible (unique) tokens or NFTs, are the two most important, covering the two fundamental token types and underpinning much of the token ecosystem, from cryptocurrencies and DeFi to NFTs. Though standards themselves are rarely in the spotlight, they're what let the vast variety of tokens and tools function as a connected whole. For anyone creating or working with tokens, following the appropriate standard is essential to building tokens that work in the ecosystem, which is exactly why token standards matter so much.
Creating or working with tokens and want them built correctly to standards? Book a free consultation with ATH Infosystems' blockchain experts today.