What Is a Bitcoin Block? Structure, Reward and Height
What is a Bitcoin block? Learn what a block contains, how miners create one, and what block height, the block reward and confirmations really mean.
A Bitcoin block is a batch of confirmed transactions bundled with a small header that links it to the previous block and proves that real computational work was spent to create it. A new block is added roughly every 10 minutes, and each one extends the shared ledger known as the blockchain.
What is inside a block
Every block has two parts: an 80-byte header and a list of transactions. The header is tiny, but it does most of the security work. It contains:
- Version: signals which consensus rules and soft-fork proposals the miner supports.
- Previous block hash: the fingerprint of the block before it. This is the link that turns individual blocks into a chain.
- Merkle root: a single hash that commits to every transaction in the block. Change one byte of one transaction and the root changes.
- Timestamp: the approximate time the miner started working on the block.
- Bits: a compact encoding of the current target, which is how the network expresses difficulty.
- Nonce: a number miners change over and over while searching for a valid hash.
The first transaction in every block is special: the coinbase transaction. It has no inputs and creates new bitcoin out of nothing to pay the miner the block reward. Everything after it is ordinary transactions taken from the mempool.
Since the SegWit upgrade, block size is measured in weight rather than raw bytes. The limit is 4,000,000 weight units, which allows blocks somewhat larger than the old 1 MB limit; the exact size in bytes depends on the mix of transactions inside.
How a block gets mined
To publish a block, a miner must find a header whose double SHA-256 hash falls below the current target. There is no shortcut: the only way is to try an enormous number of candidates, tweaking the nonce and other fields each time. At the time of writing (October 2026), the whole network performs on the order of 1 zettahash per second (about 1,000 EH/s) — a billion trillion attempts every second.
When a miner finds a valid hash, it broadcasts the block. Every other node checks the rules independently: the proof of work, the signatures, that no coin is spent twice, that the reward is not too large and that the block respects the weight limit. If everything checks out, nodes add it to their copy of the chain and miners start working on the next one.
Most blocks today are found by mining pools, which combine the hashrate of many machines and share the rewards among their members.
Block height, reward and confirmations
Block height is a block's position in the chain. The genesis block, mined on 3 January 2009, is height 0. At the time of writing the chain is around height 971,400, and the round-number milestone of block 1,000,000 is expected around late April 2027.
The block reward has two parts: the subsidy (newly created bitcoin) and the transaction fees paid by every transaction in the block. The subsidy is currently 3.125 BTC and is cut in half every 210,000 blocks in an event called the halving. Newly created coins cannot be spent until another 100 blocks have been built on top.
Each block built on top of the one containing your transaction counts as a confirmation. The deeper a transaction is buried, the more work an attacker would need to redo to reverse it, which is why exchanges and merchants often wait for several confirmations before treating large payments as final.
Frequently asked questions
Can two blocks be found at the same time?
Yes. Occasionally two miners find valid blocks at the same height within seconds of each other. Nodes briefly see two competing tips until the next block extends one of them; the other becomes a stale block, and any of its transactions that are not in the winning branch return to the mempool.
Can a block be empty?
A block must contain at least the coinbase transaction, but nothing else is required. Miners sometimes publish near-empty blocks right after a new block arrives, before they have finished validating it and building a full template.
Where can I see blocks in real time?
FreeBTC's live block feed shows each new block, the pool that mined it and how long it took. For a deeper technical view, mempool.space is a well-known open-source explorer.
On FreeBTC, every real Bitcoin block is a round of the game. Before the next one arrives, you predict which pool will mine it, whether it will come in under 10 minutes and whether its median fee will rise. Knowing what a block is makes those calls far better informed — start playing and test your reading of the chain.