Unit 1 · Level 2 · Ethereum & the EVM world
Token standards
In 2015 a proposal called ERC-20 defined a common rulebook for tokens on Ethereum: the same functions, the same events, for every token. Suddenly one wallet integration supported thousands of tokens: USB, but for money. ERC-721 followed in 2018 for one-of-a-kind tokens (NFTs), popularised by a certain cat-breeding game. Standards are boring, and they are also why any of this composes.
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What you get asked
What is ERC-20?
ERC-20 defines the standard interface (transfer, balance, approve) that fungible tokens implement. Stablecoins, governance tokens, most of DeFi: all ERC-20.
How is ERC-721 different from ERC-20?
ERC-20 tokens are like euro coins: any one is as good as another. Each ERC-721 token has its own ID, which is what makes NFTs 'non-fungible'.
Match each standard idea to what it gives you
The payoff is that everything speaking the same interface can plug into everything else, no matter who built it.
Because every ERC-20 token exposes the same functions, an exchange can list a new one without writing custom ___.
That's what standards buy: integrate the interface once, and every conforming token just works.
A token 'follows the ERC-20 standard'. What does that tell you about its quality?
Any scam can implement ERC-20 in an afternoon; it's an interface, not a seal of approval. The standard tells you how a token plugs in, never whether it's worth anything. 🐜
The rest of this unit
A gas-powered world computer, and the standard half of crypto copied.