parachain

A parachain is a blockchain that runs in parallel to a relay chain within a connected network such as Polkadot or Kusama. Parachains are sovereign networks with their own logic, governance, and tokens, but they rely on the relay chain for shared security and interoperability with the broader ecosystem. By connecting to the relay chain, parachains participate in a unified consensus system while preserving control over their own state transitions.

Architecturally, the relay chain handles global consensus and security for the ecosystem, while each parachain maintains its own state, runtime, and block production. Parachains exchange information and assets with the relay chain and with other parachains using Cross-Chain Message Passing (XCMP), a framework for interchain communication. This setup enables scalable multi-chain interoperability without each chain needing to implement its own security model.

Getting a parachain slot typically requires participating in an auction or crowdloan, where projects raise funds from the community to win a dedicated slot on the relay chain for a fixed period. Kusama commonly hosts initial parachain auctions as a canary network, with Polkadot following. In addition to fixed-slot parachains, there is also the option of parathreads, which provide pay-as-you-go connectivity to the relay chain without a permanent slot, sharing security on a on-demand basis.

Parachains are used to host specialized networks—such as those focusing on DeFi, identity, or data markets—while benefiting from shared security and cross-chain interoperability. This model aims to improve scalability and flexibility by enabling many application-specific blockchains to operate in parallel under a single overarching security framework.