What Is an ERC-20 Token?

ERC-20 is the technical standard that lets thousands of tokens live on Ethereum and work the same way across wallets and exchanges. Here's what that means in plain language.

ERC-20 in Plain Language

ERC-20 is a set of rules for creating fungible tokens on the Ethereum network. "ERC" stands for Ethereum Request for Comments, and 20 is simply the proposal number. The standard was introduced in 2015 and formally adopted in 2017.

"Fungible" means every unit is identical and interchangeable, just like dollars. One USDC equals any other USDC. This is the opposite of a non-fungible token (NFT), where each item is unique. ERC-20 is the standard behind most of the well-known coins you see traded that are not their own blockchains.

How an ERC-20 Token Is Built

An ERC-20 token is not a separate piece of software you download. It is a smart contract: a program deployed on Ethereum that keeps a ledger of who owns how much. The "standard" part means the contract must include a specific set of functions so that any wallet or exchange knows how to interact with it.

The core functions every compliant contract implements are:

Because the interface is fixed, building a token is relatively straightforward, and that is both a strength and a caution. Creating a token does not require deep infrastructure, so the existence of an ERC-20 token says nothing about whether a project is legitimate or valuable.

One important detail for beginners: token transfers cost gas fees, paid in ETH, not in the token itself. If you hold USDC but have no ETH in your wallet, you cannot move that USDC until you add some ETH for fees.

Where Wallets and Exchanges Fit In

The biggest practical benefit of ERC-20 is interoperability. Any wallet or exchange that supports the standard can support almost every ERC-20 token automatically, without custom code for each one.

• Wallets like MetaMask, Ledger, or Trust Wallet can hold any ERC-20 token. Sometimes you must "add" a token by pasting its contract address, but the underlying support is built in.
• Exchanges list ERC-20 tokens easily because deposits and withdrawals use the same standard functions.
• DeFi apps across decentralized finance are designed around ERC-20, which is why lending, swapping, and liquidity pools work with so many tokens.

ERC-20 vs Tokens on Other Chains

ERC-20 is the most established token standard, but Ethereum is not the only home for tokens. Other blockchains have their own equivalents. The ideas are similar; the standards and fee tokens differ.

A key point: the same project can issue tokens on multiple chains. USDT, for example, exists as an ERC-20 token on Ethereum and also as a TRC-20 token on Tron. They share a name but live on different networks, so you must send and receive them on the matching network. To understand why these networks behave differently, it helps to know how a blockchain works and the trade-offs in proof of work vs proof of stake.

What Beginners Should Keep in Mind

Understanding the standard is not the same as evaluating a token. ERC-20 only guarantees a token behaves in a standard way, not that it is safe, useful, or a good purchase. Here is a sensible order of questions before touching any token:

1. Confirm the official contract address and that the token is what it claims to be.
2. Look at the project's tokenomics and market cap rather than the price alone.
3. Watch for common red flags covered in guides on avoiding crypto scams, such as anonymous teams or pressure to buy quickly.
4. Keep some ETH on hand for gas, and never send more than you can afford to lose.

Crypto assets are volatile and can lose value. Nothing here is a prediction or a recommendation. ERC-20 is plumbing, a shared standard that makes Ethereum tokens work together. Knowing how that plumbing works is a solid foundation, but every individual token still deserves its own careful, skeptical research.