Coinbase Transaction
The coinbase transaction is the first entry of every block: it creates new coins and collects the fees. It is the very thing a pool assembles when it builds a block.
What a coinbase transaction is
A regular transaction has inputs: coins that somebody is spending. A coinbase has none, it creates coins out of a network rule: the block subsidy plus all the fees from transactions that made it into the block. Where that sum goes is decided by whoever assembled the block, meaning the pool or a solo miner.
On Bitcoin the coinbase reward matures for 100 blocks: freshly created coins can be spent only after a hundred confirmations on top. The rule insures the network against orphans: the block got reversed, the coins vanished, and it is a good thing nobody had managed to spend them further yet.
For a miner on a pool this explains delayed credits. The pool receives the reward not at the moment of the find but a hundred blocks later, and immature sums hang in the stats as a separate line. Schemes like PPS hide that wait from you behind the pool fee.
Inside the coinbase there is a free field, and it lives a busy life: pools write their tags there, and the extranonce goes there too, widening the search space. The field changes, the Merkle root changes, and the workers receive a fresh job.
The short version in a table
| What it creates | the block subsidy plus fees |
| Inputs | none, coins come from a network rule |
| Maturity on Bitcoin | 100 blocks before spending rights |
| Who picks the address | whoever built the block: pool or solo miner |
| What sits in the field | pool tags and the extranonce |
Where this touches a miner
An immature reward in pool stats is not a payout delay, it is a network rule: a hundred blocks of waiting are baked into the protocol.
The pool tag in the coinbase shows up in any explorer: that is how you check who found a block and how pools prove their finds.
Solo, you set the coinbase address yourself in the node settings: a mistake in that address means a reward nobody will ever receive.
Fees inside the reward are visible right there: on busy days their share noticeably lifts the value of every block found.
An example from the explorer
In a fresh block the first transaction has no inputs: subsidy plus fees in one output to the pool's address, with the pool signature and service bytes in the free field. The pool can spend that sum only after 100 blocks, so for now it hangs in its stats as immature.
Related terms
Where to go next on the site
Coins
- Bitcoin coins
Numbers
Questions and answers
Why doesn't the pool pay right after a found block
The reward matures for 100 blocks by network rule. Pools running PPS pay from their own reserve without waiting for maturity, and that is exactly why they charge a higher fee.
Can a coinbase become invalid
Yes, together with its block: if it became an orphan, the created coins no longer exist. That is what the 100 block maturity was invented for.
What do pools write in the free field
Their tag, service data, and the extranonce. Those tags are what explorers use to build stats on which pool found how many blocks.
How the terms connect
Every link in the chain is clickable. Orange marks where you are now.
Looking for an ASIC miner
The catalog holds 212 models. You can compare them by hashrate and by joules per terahash, then plug your own rate into the calculator and see what stays in your pocket.
Page written and checked by Denys Klimchuk. Updated .