Glossary
Layer 0
The foundational interoperability layer beneath individual blockchains that lets independent Layer 1s launch, exchange messages, and sometimes share a pooled security base.
A Layer 0 is the base infrastructure that sits underneath Layer 1 blockchains, providing the shared plumbing that lets many independent chains launch, talk to each other, and move assets across boundaries. Rather than settling transactions itself, it defines the protocols, messaging standards, and sometimes the pooled security that the chains built on top depend on.
Polkadot's relay chain, the Cosmos SDK with IBC, Avalanche's subnet framework, and cross-chain messaging networks like LayerZero are all described as Layer 0. The promise is interoperability without forcing every application onto a single chain: developers spin up purpose-built Layer 1s that inherit connectivity — and occasionally security — from the layer beneath them.