ERC-20 (Ethereum Token Standard)

ERC-20 is a technical standard on the Ethereum blockchain that defines how a fungible token should behave. Fungible means every unit is identical and interchangeable — one token of a given ERC-20 is worth exactly the same as any other of that token, and it can be divided into fractions, just like a dollar or a share. The standard, proposed by Fabian Vogelsteller in 2015, does this by specifying a common set of functions and events every compliant token must implement — how to check a balance, transfer tokens, approve another address to spend on your behalf, and read the total supply. Because the interface is fixed, any wallet, exchange, or application that understands ERC-20 can handle every ERC-20 token without custom code for each one.

That standardization is the whole point. Before agreed interfaces, each token could work differently, and integrating one meant bespoke engineering. ERC-20 turned tokens into interoperable building blocks: a new project can issue a token and instantly be listed, held, and traded across the vast infrastructure that already speaks the standard. Most utility tokens, governance tokens, and many stablecoins are ERC-20s. The standard does not dictate what a token is for or what it is worth — it only guarantees how it behaves — so an ERC-20 can represent almost anything a project chooses, provided the value proposition holds up outside the code. None of this is financial advice.

The clearest way to understand ERC-20 is against its non-fungible sibling, ERC-721. ERC-20 tokens are fungible — interchangeable and divisible — so they suit currencies, points, and shares of a pool, anything where one unit is as good as another. ERC-721, introduced in 2018, is the standard for non-fungible tokens (NFTs), where each token is unique, indivisible, and carries its own identity. An ERC-721 token is right for a specific collectible, a deed to one item, or a single ticket, because no two are the same. Put simply, ERC-20 is many identical coins, ERC-721 is many distinct one-of-a-kind items, and the choice depends on whether the thing you are representing is interchangeable or unique.

There are further standards for cases that fall between, such as ERC-1155, which lets a single contract manage both fungible and non-fungible tokens together — handy for a game with both currency and unique items. But the core distinction is fungibility. ERC-20 answers "how do interchangeable tokens behave," ERC-721 answers "how do unique tokens behave," and mixing them up leads to the wrong contract for the job — trying to issue a collectible as an ERC-20 loses its uniqueness, and issuing a currency as ERC-721 makes it non-divisible and unusable as money. Pick the standard that matches whether your asset is interchangeable.

For a marketing or product team touching tokens — a loyalty point, a community token, an access credential — ERC-20 is usually the right primitive when the units are meant to be interchangeable and divisible, because it plugs into existing wallets, exchanges, and tooling with no custom integration. The practical benefit is reach and composability: an ERC-20 can move through the whole Ethereum ecosystem the day it launches. Understand the standard's mechanics too, especially the approve-and-transfer pattern, where a user grants an app permission to move a set amount of their tokens, because unlimited approvals are a common source of drained wallets when the approved contract is malicious or compromised.

The failure modes are mostly about mismatch and misplaced trust. Choosing ERC-20 for something genuinely unique, where ERC-721 belongs, strips the uniqueness the asset needs. Assuming the standard confers any value is another trap — ERC-20 guarantees behavior, not worth, and a compliant token can be worthless or a scam. Granting unlimited spending approvals to unverified contracts risks the whole balance. And treating a token's compliance as a stamp of legitimacy ignores that anyone can mint an ERC-20 in minutes. The standard is plumbing; sound judgment about what the token represents and who you trust with it still has to come from you. This is not financial advice.

ERC-20, proposed by Fabian Vogelsteller in 2015 as Ethereum Request for Comments number 20, became the dominant standard for fungible tokens on Ethereum.

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