Blockchain & Web3

All Ethereum JSON-RPC APIs (Infura, Alchemy, local nodes, MetaMask) use JSON-RPC 2.0. You need to know the protocol to interact with EVM chains.

Understanding EIP-1 gives you the map for reading all other EIPs. Know which type a given EIP is (Core, Networking, Interface, ERC) and what Final vs Draft status means.

ERC-20 is the most widely deployed standard in the Ethereum ecosystem. Every DeFi integration, exchange, and wallet interacts with ERC-20 tokens constantly.

NFTs, digital ownership, gaming assets, and on-chain certificates all use ERC-721. The standard that launched the NFT market.

EIP-712 is the standard for secure off-chain message signing used in permit() flows, meta-transactions, and Sign-In with Ethereum. Prevents blind signing attacks.

EIP-1559 is how Ethereum gas fees work since London fork (2021). Required knowledge for estimating transaction costs, building gas estimation into apps, and understanding ETH supply.

SIWE is the Web3 equivalent of Sign-In with Google. Enables dApps to authenticate users via their Ethereum address without a password, using their wallet signature.

Every modern cryptocurrency wallet (Ledger, Trezor, MetaMask, Coinbase Wallet) uses BIP-32 for key derivation. The foundation of the seed phrase model.

Seed phrases are the primary backup mechanism for all HD wallets. BIP-39 defines the 12/24 word format, wordlist, and checksum — everything about the backup experience.

Derivation paths determine which addresses you get from a seed phrase on each chain. BIP-44 paths (m/44'/60'/0'/0/0 for ETH) explain why the same seed gives different addresses on different wallets.

EIP-4337 is the deployed standard powering smart wallets across Base, Optimism, Arbitrum, and Polygon (Coinbase Smart Wallet, Safe{Core}, Biconomy, Pimlico, Alchemy AA). Required knowledge for building AI agents that pay gas through Paymasters, gasless onboarding flows, and any wallet experience that doesn't start with "buy ETH first."

DIDs are the foundation of self-sovereign identity (SSI) and Web3 identity. They underpin Verifiable Credentials, Sign-In with Ethereum, and many blockchain identity schemes.

The W3C standard for digital credentials. Increasingly important for identity verification, age proofs, academic credentials, and government ID use cases.

More gas-efficient than deploying separate ERC-20 + ERC-721 contracts. Standard for gaming, semi-fungible assets, and multi-edition NFTs.

Every NFT's display (image, name, description, traits) is driven by this metadata schema. Off-chain storage of this JSON (IPFS, Arweave, HTTP) is a critical design decision.

EIP-191 is the foundation under every off-chain Ethereum signature you've ever validated — personal_sign, EIP-712, SIWE, x402, EIP-3009, and EIP-2612 all sit on top of it. Knowing the version bytes is essential when verifying signatures server-side or debugging signature mismatches.

EIP-2612 is how DEXes, lending protocols, and meta-tx relayers achieve gasless approvals. If you're integrating ERC-20s into any UX where the user shouldn't need ETH first, permit() is the canonical solution. DAI, USDC, and most modern stablecoins implement it.

EIP-3009 is the gasless transfer primitive USDC uses on Ethereum and Base. It's the on-chain mechanism behind the x402 "exact" scheme: the buyer signs an authorization, the seller (or facilitator) submits it on-chain to settle. If you're building anything that spends USDC on behalf of a user without them paying gas, this is the spec.