Block 1 – The Coinbase Transaction

Raw Serialized Form – Coinbase Transaction (153 bytes)

This is the exact byte-for-byte content that appears after the block header and the 1-byte transaction count (01).

What is a Coinbase Transaction?

A coinbase transaction is how new bitcoins are created in every block. It has no real "from" address — it mints brand-new coins as a reward for the miner who solved the block puzzle.

In Block 1 there is only one transaction — this coinbase — which created the second 50 BTC (the first truly spendable reward after genesis).

Key Properties of the Block 1 Coinbase

• Creates exactly 50 BTC (the original block reward)
• Contains no real previous output (uses all-zeros dummy input)
• No embedded newspaper headline or message — unlike genesis, just minimal data: difficulty bits push + 0x01 + 0x04
• Uses the old Pay-to-Public-Key (P2PK) output style (full public key in script)
• The 50 BTC are fully spendable — no special exception exists for Block 1; added to the UTXO set normally after maturity

How the Raw Public Key Becomes the Familiar Address

Block 1's coinbase doesn't use a modern Bitcoin address in its output script. It places the full public key directly into the locking script (P2PK style), just like genesis. Block explorers display this as a familiar address starting with "1" for convenience.

Here's exactly how that address is derived from the raw public key — step by step.

The Starting Point: Raw Uncompressed Public Key (65 bytes)

0496b538e853519c726a2c91e61ec11600ae1390813a627c66fb8be7947be63c52da7589379515d4e0a604f8141781e62294721166bf621e73a82cbf2342c858ee

This 65-byte value begins with 04 (the marker for uncompressed format) and is the actual cryptographic public key embedded in the Block 1 coinbase output.

Step 1: Compute SHA-256 of the public key

6527751dd9b3c2e5a2ee74db57531ae419c786f5b54c165d21cdddf04735281f

Step 2: Compute RIPEMD-160 of that SHA-256 result

This produces a 20-byte value called the hash160 (also called pubkey hash):

119b098e2e980a229e139a9ed01a469e518e6f26

This 20-byte hash is the core of most legacy Bitcoin addresses.

Step 3: Add the version byte (mainnet = 0x00)

00119b098e2e980a229e139a9ed01a469e518e6f26

The leading 00 tells software this is a standard P2PKH address on the Bitcoin main network.

Step 4: Compute the checksum (first 4 bytes of double SHA-256)

Double-hash the 21 bytes above (SHA-256 twice) and take the first 4 bytes, then append them. First SHA 256 gives:

d304d9060026d2c5aed09b330b85a8ff10926ac432c7a7aee384e47b2fa1a670

Second SHA 256 gives:

90afe11c54d3bf6bacd6bf92a3f46eecbe9316dc1af9287791a25d340e67f535

First 4 bytes:

90afe11c

Step 5: Append the checksum and Base58Check encode

00119b098e2e980a229e139a9ed01a469e518e6f2690afe11c

Convert the resulting 25-byte string into Base58Check format (the friendly string that avoids confusing characters like 0/O, I/l). The resulting derived address, as confirmed by block explorers, is:

12c6DSiU4Rq3P4ZxziKxzrL5LmMBrzjrJX

This is the address as seen at: Block 1 coinbase on Mempool

Key Things to Understand

• Block 1 uses the full public key in its script — not the address.
• The address 12c6DSiU4Rq3P4ZxziKxzrL5LmMBrzjrJX is what explorers and wallets derive and display for convenience.
• Any modern P2PKH address is created the same way: public key → hash160 → version + checksum → Base58Check.
• Unlike genesis, this reward was added to the UTXO set and became spendable with the corresponding private key.

Summary

The transaction in Block 1 is a simple, standard coinbase (~153 bytes). It:

• Mints the second 50 bitcoins
• Uses minimal coinbase data with no embedded headline
• Continues the P2PK output format from genesis
• Creates the first truly spendable block reward

This transaction marks the real beginning of mining new coins on the live Bitcoin network.