What is an ERC-20 Token? A Complete Beginner's Guide

ERC-20 is the most important token standard in crypto. The vast majority of tokens you've heard of — stablecoins, governance tokens, meme coins and utility tokens — are ERC-20 tokens. But what does that actually mean? This guide explains the standard in plain language, shows what happens under the hood, and explains why it became the foundation of the token economy.

The standard, in one sentence

ERC-20 is a shared rulebook that every fungible token on Ethereum agrees to follow. Because every compliant token exposes the same functions, any wallet, exchange or app can support all of them at once without custom code per token. Build to the standard and your token instantly plugs into the entire ecosystem.

What "fungible" means

Fungible means interchangeable. Every unit of an ERC-20 token is identical to every other unit — one token equals one token, just like one ten-dollar bill is worth the same as any other. This is the opposite of an NFT (a "non-fungible token"), where each item is unique. Fungibility is what makes ERC-20 tokens suitable as currencies, shares, points and rewards.

The core functions

The standard defines a handful of functions and two events. You don't need to memorise them, but understanding what they do demystifies how tokens move:

The two events — Transfer and Approval — are logs emitted on-chain so wallets and explorers can track movements and balances in real time.

Why approvals exist

A common question for newcomers is why DeFi asks for an "approval" before a swap. ERC-20 tokens can't be pushed directly into a contract; instead you approve the contract to pull a certain amount, then it calls transferFrom. This two-step model is powerful but worth understanding — granting unlimited approvals to unknown contracts is a common source of risk, so revoke approvals you no longer use.

Decimals and how balances are stored

ERC-20 tokens store balances as whole numbers and use a decimals value to tell wallets where to put the decimal point. The standard default is 18, mirroring ETH. So a balance of "1 token" is actually stored as 1 followed by 18 zeros internally. This is invisible to users but important for developers and when adding liquidity. Learn more in choosing supply and decimals.

What ERC-20 does *not* guarantee

This is the most important section for anyone evaluating a token. The standard guarantees the interface — not the behaviour. Two tokens can both be valid ERC-20s while behaving very differently inside:

• One might have a fixed supply and no owner; another might let its owner mint unlimited new tokens.
• One might transfer freely; another might be pausable or apply a transfer tax.
• One might be immutable; another might have an owner who can change parameters.

That's why you should always check a token's contract and ownership before trusting it. Our guides on why immutable tokens are safer and the ERC-20 token security guide go deeper.

Where ERC-20 tokens live and trade

Because they share a standard, ERC-20 tokens are supported across the board: MetaMask and every major wallet, DEXs like Uniswap and Curve, centralized exchanges, portfolio trackers and block explorers like Etherscan. A new token created today works with all of these immediately — no integrations required.

Creating your own ERC-20

You don't need to write Solidity to launch an ERC-20. Tools like Create ERC-20 Token let you set a name, symbol and supply and deploy a verified contract in a single transaction. Follow our step-by-step creation guide to do it in about a minute.

Conclusion

ERC-20 is the common language of fungible tokens on Ethereum. It defines a simple, shared interface that lets every wallet and app support every compliant token — which is exactly why it powers most of crypto. Just remember that the standard governs how a token connects, not how it behaves: always look at the contract before you trust it.

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