About block 921,312
Bitcoin block 921,312 was mined by ViaBTC on October 29, 2025 at 10:14 AM UTC, 5 min 34 s after block 921,311. That is faster than the 10-minute average the network aims for: blocks come in bursts because finding one is pure chance.
It confirmed 1,240 transactions in 0.56 MB (32.1% of the 4 million weight-unit limit). The median transaction paid 1.00 sat/vB, up from 1.00 sat/vB in the block before, and all fees added up to 0.0105 BTC. With the 3.125 BTC subsidy of halving era 5, ViaBTC earned 3.1355 BTC for this block.
Block 921,312 is number 1 of 2,016 in difficulty epoch 457; 2,015 blocks remain until the next difficulty adjustment at block 923,327. The next halving is at block 1,050,000, 128,688 blocks after this one.
Its hash starts with 20 zeros: that is the proof of work, a number below the target that the whole network’s hashrate had to search for. ViaBTC found 82 blocks in the week before. Today the block has 52,214 confirmations, so it is settled beyond any practical doubt.
Why block 921,312 is notable
Block 921,312 opens difficulty epoch 457. 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, 155,973,032,196,072, took effect with this block, found by ViaBTC on October 29, 2025 at 10:14 AM UTC, and applies until block 923,327; the following adjustment is at block 923,328.
Nobody schedules a retarget. It happens when the chain reaches the height, so the adjustment at block 921,312 came the moment ViaBTC 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.
Of the 3.13548563 BTC that ViaBTC collected for this block, 3.125 BTC was new subsidy and 0.01048563 BTC came from fees, 0.3% of the total; leaving out the coinbase, its 1,239 transactions paid about 846 sats each on average.
Current difficulty epoch and next adjustment →
What’s inside a Bitcoin block
Every block, 921,312 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 921,312 holds 1,240, 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 921,312 it is 3.125 BTC.