Parachain

Parachains are independent, application-specific chains that connect to Polkadot's relay chain to share in its pooled validator security and cross-chain messaging, rather than each having to recruit and pay its own set of validators. Because the relay chain handles consensus and finality for every connected chain, a parachain team can focus its engineering effort on a custom runtime, whether that is a DeFi platform, a gaming chain, or an identity network, instead of bootstrapping security from scratch.

Access to a relay chain "core" used to be won through multi-week candle auctions, where projects locked up large amounts of DOT for lease periods of up to two years, often financed through community crowdloans. That model was retired in September 2024 in favor of Agile Coretime: teams now buy bulk coretime in monthly renewable blocks, or pay per block through on-demand coretime, both settled on a dedicated Coretime system chain. A related upgrade, elastic scaling, lets a busy parachain temporarily use several cores at once and release them when demand drops, and part of every coretime payment is burned, tying network usage directly to DOT's supply.

Parachains communicate through Cross-Consensus Messaging (XCM), which lets tokens and data move between chains without a separate bridge. Notable examples include Asset Hub, Moonbeam, and Acala. A parachain that lets its coretime lapse is downgraded to a "parathread" until it renews access.