About block 12,096
Bitcoin block 12,096 was mined by Unknown on April 24, 2009 at 6:51 PM UTC, 6 seconds after block 12,095. That is faster than the 10-minute average the network aims for: blocks come in bursts because finding one is pure chance.
It confirmed 1 transactions in 0.00 MB (0.0% of the 4 million weight-unit limit). The median transaction paid 0.00 sat/vB, and all fees added up to 0.0000 BTC. With the 50.000 BTC subsidy of halving era 1, Unknown earned 50.0000 BTC for this block.
Block 12,096 is number 1 of 2,016 in difficulty epoch 6; 2,015 blocks remain until the next difficulty adjustment at block 14,111. The next halving is at block 210,000, 197,904 blocks after this one.
Its hash starts with 8 zeros: that is the proof of work, a number below the target that the whole network’s hashrate had to search for. Unknown found 3 blocks in the week before. Today the block has 963,544 confirmations, so it is settled beyond any practical doubt.
Why block 12,096 is notable
Block 12,096 opens difficulty epoch 6. Every 2,016 blocks, each node recalculates the mining difficulty from how long the previous epoch took: if those blocks arrived in less than two weeks, difficulty goes up; if they took longer, it goes down, never by more than a factor of four. The new value, 1, took effect with this block, found by Unknown on April 24, 2009 at 6:51 PM UTC, and applies until block 14,111; the following adjustment is at block 14,112.
Nobody schedules a retarget. It happens when the chain reaches the height, so the adjustment at block 12,096 came the moment Unknown found it, not on a fixed date. The rule keeps the average close to one block every ten minutes however much hashrate joins or leaves the network.
Current difficulty epoch and next adjustment →
What’s inside a Bitcoin block
Every block, 12,096 included, is made of the same parts:
- Header
- Eighty bytes that miners hash over and over: the version, the hash of the previous block, the Merkle root that summarises every transaction, a timestamp, the difficulty target in compact form and a nonce. A block is valid when the hash of its header falls below the target.
- Coinbase transaction
- The first transaction, written by the miner. It spends no inputs: it creates the subsidy and collects the fees, and since BIP 34 it must also record the block height.
- Transactions
- Everything else in the block: payments taken from the mempool, usually picked by fee rate because space is capped at 4 million weight units. Block 12,096 holds 1, counting the coinbase.
- Fees
- The difference between what each transaction spends and what it creates. The miner claims them in the coinbase; they are the part of the reward set by demand rather than by the protocol.
- Subsidy
- New bitcoin created by the block, fixed by the halving schedule: 50 BTC at the start, halved every 210,000 blocks. At height 12,096 it is 50 BTC.