Block explorers: Etherscan basics
Teach what a block explorer is and how to look up a transaction, address, or contract.
Lesson path
Crypto and DeFi
On-Chain Basics
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Teach what a block explorer is and how to look up a transaction, address, or contract.
Your free X-ray machine for the chain
A block explorer is a website that lets you search the blockchain like Google searches the web. Paste in a wallet address, a transaction hash, a token contract, or a block number, and the explorer shows you everything about it. The most popular block explorers are Etherscan (for Ethereum and its tokens), Solscan (for Solana), Mempool.space (for Bitcoin), and Arbiscan (for Arbitrum). You don't need an account. You don't pay anything. Everything you see is public data — the explorer is just a friendly window into it.
What can you actually do? Paste an address and you see balance, every transaction in and out, every token held, every NFT, every DeFi position. Paste a transaction hash (the long string starting with 0x your wallet shows after every send) and you see exactly what happened — which contracts got called, how much gas was used, whether anything failed, and what state changed. Paste a token contract and you see total supply, top holders, and trade history.
For new traders, three habits make block explorers a real edge. First, after every transaction you send, copy the transaction hash from your wallet and paste it into Etherscan. Confirm it landed, confirm it did what you expected, confirm gas was reasonable. Second, before interacting with any new token contract, paste it into Etherscan and look at the holder distribution and the source code (if verified). Top three holders own 90 percent? Red flag. Third, when you see a wallet on Twitter or in a Telegram group claiming big trades, you can verify by pasting their address and checking yourself.
A note on the 'Internal Txns' tab on Etherscan: regular transactions are what you initiated, but most DeFi swaps trigger a cascade of follow-up calls between contracts. Those show up under Internal Txns. If your transaction looks normal at the top but you can't figure out where the money actually went, the Internal Txns tab usually tells you.
Recap: a block explorer is a public search engine for the blockchain. Paste a hash, address, or contract. See everything. Use it after every transaction. Use it before interacting with new tokens. Verify claims, don't trust screenshots.
Knowledge check
Answer before moving on.
1. A friend texts you a screenshot of a 10,000-dollar profit on a memecoin. What's the strongest way to verify?
2. Which block explorer would you use to look up a Bitcoin transaction?
3. Your DeFi swap shows in your wallet as confirmed, but you can't see where your output token went. Where do you check?
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