# coinbase transaction

URL: https://blockspace.wiki/glossary/coinbase-transaction/

The first transaction of every [block](https://blockspace.wiki/glossary/block/), written by the miner. Its input has no previous output to spend, and its scriptSig is 2 to 100 bytes and must begin with the block height (BIP 34). After segwit it also carries the witness commitment. Miners pay no fee to themselves on it. Sats a coinbase never claimed are [lost sats](https://blockspace.wiki/glossary/lost-sats/).

Sources:

- block.space docs: data types · https://block.space/docs/datatypes
- The blockspacelabs.com page (index.html) · https://blockspacelabs.com

Updated: 2026-10-20