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A public ledger everyone can read

Public ledger concept — shared record of Bitcoin transactions

Every Bitcoin transaction ever made is written in a shared record — no bank owns the notebook.

Imagine a notebook that everyone can read but no one can erase. That is Bitcoin's public ledger — the blockchain. Unlike your bank app where only the bank sees the full history, Bitcoin's record is open to the world.

Priya

So when I sent sats, it went into a book the whole world can check?

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Blocks linked in a chain

New transactions group into blocks — each block links to the one before it.

Block

Previous hash

Transactions

Chain

New transactions are bundled into blocks. Each block contains a fingerprint of the previous block — forming a chain. Change one old entry and every block after it would need to be rebuilt. Hence: block-chain.

Dadi

Like numbered pages in a ledger, beta — tear one out and the whole book screams.

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Transactions live inside blocks

Transactions bundled into a block awaiting confirmation

Your UTXO spend joins others in a block — miners compete to add the next one.

Inside a block

1Collect txs
2Bundle block
3Solve puzzle
4Broadcast

When you broadcast a signed transaction, it waits in a mempool until miners bundle it into a block. A block might hold hundreds of transactions — each one spending UTXOs and creating new outputs, just as you learned in the UTXO quest.

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Confirmations make it final

Confirmation count growing as more blocks stack on the chain

One confirmation is fast — six confirmations is the gold standard for larger amounts.

1 confirmation

~10 minutes
Small payments OK

6 confirmations

~1 hour
Safer for larger amounts

Once a block is added, your transaction has one confirmation. Each new block on top adds another. For small amounts, one or two may suffice. For larger savings, wallets often wait for six confirmations — roughly an hour — before treating payment as settled.

Priya

So I wait a bit before calling a payment "done" — like waiting for a UPI SMS?

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Immutability — history that resists edits

Immutable blockchain history protected by distributed verification

To rewrite one old transaction, an attacker must redo work for every block after it — across the globe.

This chain design gives immutability. No CEO can reverse your payment. No government can quietly edit the ledger. The 21 million cap and every UTXO spend are recorded in history that thousands of nodes independently verify.

You now know where transactions live. Next quests explore who secures the chain and how.

Dadi

Slow can be strong, beta. A ledger nobody can secretly rewrite is worth understanding.

How Does Bitcoin Work?

Before you start

A public ledger everyone can read

Blocks linked in a chain

Transactions live inside blocks

Confirmations make it final

Immutability — history that resists edits

✅ Key takeaway

Quest Challenge