Layer 0 is a term for the infrastructure that sits underneath individual blockchains and lets developers launch and connect their own chains. A layer-0 network typically supplies some combination of shared security, a common framework for building chains, and a way for those chains to pass messages and tokens to each other. The chains built on it are layer-1 blockchains in their own right, with their own rules and tokens.
The idea grew out of the search for blockchain interoperability and scaling. Rather than forcing every application onto one crowded chain, layer-0 projects such as Polkadot, Cosmos and, in some descriptions, Avalanche encourage many specialised chains that work together. The label is informal and marketing-heavy: in older networking usage, "layer 0" can also mean the physical hardware and internet links that all blockchains run over.
Layer 0 in plain terms
Think of a shopping centre. Each shop has its own staff, stock and prices, but the building, the security guards, the car park and the corridors between shops are shared. A layer-0 network is the shopping centre; the individual blockchains are the shops. Someone opening a new shop does not need to build a whole new building, and customers can walk from one shop to another without going back outside.
In blockchain terms, the "building" might provide protection against attackers, standard tools for setting up a new chain, and a safe corridor for moving coins and messages between chains. The trade-off is that every shop depends on the centre: if the shared parts fail, all of them are affected.
How layer-0 networks work
Designs differ, but most layer-0 systems combine three elements:
- A base chain or hub. Polkadot's relay chain coordinates connected chains and provides their security; in Cosmos, hubs and zones connect through a common protocol.
- A development framework. Toolkits such as Polkadot's Substrate and the Cosmos SDK let teams launch a chain with a ready-made consensus mechanism, networking and account system.
- A messaging standard. Cosmos chains talk through Inter-Blockchain Communication (IBC), while Polkadot uses its own cross-chain messaging format.
Security models
The biggest design choice is who secures the connected chains. In a shared-security model, as on Polkadot, the validators of the base chain also check the blocks of connected chains, so a small new chain benefits from the stake behind the whole network. In a sovereign model, as in most of the Cosmos ecosystem, each chain recruits and pays its own validators, which gives more independence but means small chains can be cheaper to attack. Some Cosmos chains have since adopted forms of shared or "replicated" security. Avalanche lets groups of validators run their own chains alongside its primary network, a design it has revised over time.
Shared security is not free. Connected chains on Polkadot originally had to win slot auctions by locking up DOT for long periods, and the network has since moved towards selling block space more flexibly. Sovereign chains avoid such costs but must issue enough rewards to attract validators, which often means high inflation of their own tokens in their early years.
Layer 0, layer 1 and layer 2
| Layer | Role | Examples |
|---|---|---|
| Layer 0 | Infrastructure for building and connecting chains | Polkadot relay chain, Cosmos hub and SDK |
| Layer 1 | A base blockchain that settles transactions under its own consensus | Bitcoin, Ethereum, Solana |
| Layer 2 | A system that processes activity off the base chain and posts results back to it | Rollups, payment channels |
The categories overlap. Ethereum is a layer 1 but, with layer-2 rollups settling on it, it plays some of the coordinating role of a layer 0. Messaging protocols that connect existing chains, including one named LayerZero, are sometimes called layer-0 infrastructure even though they do not host chains themselves; these overlap with blockchain bridges.
Criticism and risks
- Complexity. Cross-chain systems add code, assumptions and attack surface. Many of the largest crypto thefts have targeted bridges and messaging layers rather than the chains themselves.
- Shared failure. A bug or outage at the base layer can affect every chain that relies on it.
- Fragmented liquidity. Spreading activity across many chains can split users and capital, partly undoing the benefit of a single shared ledger.
- Loose terminology. "Layer 0" is not a formal standard, so projects use it to mean different things, and investors can be misled by the label alone.
Supporters argue that a network of specialised chains is the most practical way around the blockchain trilemma of security, scalability and decentralisation, an approach often described as multi-chain. Rival approaches favour a single high-throughput chain or a modular stack of layer 2s on one base layer.