Merge Mining
Mining two or more blockchains simultaneously using the same proof-of-work, without needing additional hashpower beyond what securing one chain already requires.
Merge mining lets a miner work on securing a second ("auxiliary") blockchain at the same time as a primary chain, by including a commitment to the auxiliary chain's data within the primary chain's block, so the same proof-of-work (see Kaavon's "Proof of Work" glossary definition) that satisfies the primary chain's difficulty target simultaneously counts as valid work for the auxiliary chain. This means a miner can contribute hash rate to both chains without splitting their mining hardware's capacity between them.
Merge mining is typically used by a newer or smaller chain seeking to bootstrap security comparable to an established, high-hash-rate chain, since the smaller chain benefits from a much larger pool of mining power than it could attract on its own. The auxiliary chain remains dependent on miners of the primary chain choosing to merge mine it, meaning participation isn't automatic or guaranteed just because the technical capability exists.
Examples
- A newer blockchain using merge mining with Bitcoin can inherit a meaningful share of Bitcoin's enormous hash rate without needing to attract that mining power independently.
- Merge mining only provides security benefits to the auxiliary chain if a meaningful share of the primary chain's miners actually choose to participate in it.