Unit 1 · Level 1 · Block explorers
The chain is public
Your bank's ledger is a locked vault: only the bank sees the full picture. A public blockchain flips that completely. Every transaction since the very first block in 2009 sits in the open, visible to anyone with an internet connection, forever. No login, no permission, no expiry date. This unit teaches you to read that open book.
Free to play. No ads, no token, no account needed to start.
What you get asked
What can anyone, including you, see on a public blockchain?
That's the whole point of a public chain: one shared history, readable by everyone. Nothing expires and nothing needs a login.
Blockchains are called pseudonymous rather than anonymous. Why?
An address like 0x4f2a… doesn't say who you are, but everything it ever did is on display. Link the address to a person once, and their whole history opens up.
Once a transaction is buried under enough blocks, it is effectively ___: nobody can quietly edit or delete it.
Remember consensus from the Crypto course: rewriting history would mean out-muscling the entire honest network. In practice, what's written stays written.
Match each record to who can see it
The blockchain is the odd one out: it's the only ledger where a stranger in another country can audit every entry without asking anyone.
In 2022, US investigators seized roughly $3.6B of Bitcoin stolen in the 2016 Bitfinex hack. What made tracing it possible six years later?
The thieves moved coins for years, but every hop was recorded in public. Investigators just had to read patiently, because the chain never forgot. 🐜
The rest of this unit
The whole ledger is public. Learn to open it and read it.