Question Bank

Web3 & Blockchain Frontend Interview Questions

Frontend-focused web3 questions covering wallet connection (EIP-1193 and window.ethereum), reading and writing contract state with viem and wagmi, the transaction lifecycle and pending-state UX, EIP-712 typed-data signing, wei and BigInt precision, event syncing, chain switching, RPC provider strategy, approval security, ENS, and dapp testing — the material that separates real dapp engineers from tutorial-followers.

15 questions — free to read, with quizzes and AI-scored practice for members.

Web3 & Blockchain15 questions

What's the difference between a contract 'read' and a contract 'write' from a frontend perspective, and how does gas come into it?junior How would you display a user's ENS name and avatar instead of a raw 0x address, and what do you need to be careful about?junior Walk me through how a browser dapp connects to a user's wallet. What is window.ethereum, and how does the EIP-1193 provider interface fit in?mid You're building the wallet-connection layer of a React dapp. How would you model and manage connection state — address, chain, connection status — across the app?mid How do you read on-chain contract state in a React app with a library like wagmi or viem? What makes a read different from a normal REST fetch?mid A teammate displays a token balance by doing balance / 1e18 and users report tiny rounding errors on large balances. What's going wrong and how do you fix it?mid A user has your dapp open but their wallet is on the wrong network, and contract calls fail. How do you detect this and guide them to the right chain?mid A user submits a transaction that changes on-chain state. Walk me through the full lifecycle and how you'd design the UI to communicate each stage.senior What is EIP-712 typed-data signing, and why would a dapp use it instead of signing a plain string message?senior Your dapp needs to update the UI when a specific contract event fires (e.g. a Transfer to the connected user). How would you implement that, and what are the pitfalls?senior Design the RPC/data layer for a production dapp. How does the frontend talk to the blockchain reliably, and how do you handle rate limits and outages?senior Transactions in your dapp fail for many reasons — user rejection, insufficient funds, reverts, RPC errors. How do you surface these clearly instead of a generic 'transaction failed'?senior On-chain data changes every block. How do you keep a dapp's UI reasonably fresh without hammering the RPC or degrading performance?senior How would you test the frontend of a dapp — the wallet connection, reads, and a write flow — without depending on a live network and real funds?senior Many dapps request an unlimited ERC-20 approval to reduce transaction count. Discuss the security trade-offs and how you'd design the approval UX responsibly.senior

Practice these with AI feedback and track what you've mastered.

Browse other topics

JavaScript React Frontend System Design Web Performance Browser & Web APIs Testing Behavioral