Unit 1 · Level 1 · Block explorers
Anatomy of an explorer
A block explorer (Etherscan is the famous one for Ethereum, but every chain has its own) is simply a website that reads the public ledger and makes it browsable. One search box, three kinds of things to paste in: a block number, a transaction hash, or an address. Learn those three and the whole chain opens up.
Free to play. No ads, no token, no account needed to start.
What you get asked
Match each explorer term to what it is
These are your three search keys plus one coordinate. Everything an explorer shows hangs off a block, a transaction, or an address.
You paste a long 0x… string into an explorer and get the page for one specific payment. What did you search?
The tx hash is the receipt number of a single transaction: paste it in and you land on exactly that event. (And a seed phrase should never be pasted anywhere, as the Crypto course drilled in.)
Every block contains the ___ of the block before it, and that link is what forms the 'chain'.
Each block fingerprints its parent. Tamper with an old block and every fingerprint after it breaks, which is exactly why history is so hard to rewrite.
What does an address page on an explorer show you?
Balance, full history, tokens held, contracts touched: all public, no permission needed. The owner's identity is the one thing the page doesn't know.
Etherscan-style explorers don't control the blockchain. What are they, really?
An explorer is a window, not the building. The data lives on thousands of nodes; you could run one yourself and see the exact same ledger. 🐜
The rest of this unit
The whole ledger is public. Learn to open it and read it.