A mainchain is the primary blockchain in a network, the base layer that maintains the canonical ledger of transactions. It is where the network’s consensus rules are enforced, blocks are produced, and transaction finality is established. In simple terms, if a blockchain ecosystem has multiple layers, the mainchain is the “parent” chain that anchors security and truth for the system.
How a mainchain works
On the mainchain, nodes validate transactions and agree on the order of events using a consensus mechanism such as proof of work or proof of stake. Once a transaction is included in a block and that block becomes part of the accepted chain, the transaction is considered confirmed, and later finalized depending on the protocol’s rules. The mainchain also defines the network’s core parameters, for example how blocks are formed, how fees are paid, and how smart contracts execute, making it the reference point that other components must ultimately align with.
Mainchains vs layer 2 networks and sidechains
Many ecosystems expand beyond the mainchain to improve scalability or add specialized features. Layer 2 networks process activity off the mainchain, then post proofs or summaries back to the mainchain for settlement, letting users benefit from faster and cheaper transactions while relying on the mainchain for finality. Sidechains are separate blockchains connected to the mainchain through bridges, and they may have their own validators and security assumptions. For example, a user might move tokens from a mainchain to a sidechain to access an application that offers higher throughput, then bridge assets back when done.
Understanding what the mainchain is matters because it clarifies where security and final settlement come from, what risks differ across scaling solutions, and why congestion or fees on the base layer can affect the wider crypto ecosystem.