Layer 1

A Layer 1 is a blockchain that runs completely on its own, without depending on any other network to process, order, or finalize transactions. It has its own validators or miners, its own consensus rules, and its own native token used to pay fees and secure the chain. Everything else in the ecosystem, from sidechains to rollups, is built on top of one of these base layers.

Because an L1 handles transaction execution, data storage, and consensus in one place, its design is shaped by the so-called blockchain trilemma: the difficulty of maximizing security, decentralization, and scalability at the same time. Bitcoin leans toward security and decentralization through Proof of Work, accepting lower throughput as a trade-off. Ethereum moved to Proof of Stake to cut energy use and now leans on Layer 2 rollups for extra capacity while keeping the base chain as its settlement and security layer. Newer L1s like Solana and Avalanche prioritize raw speed and low fees with alternative consensus designs, often at some cost to decentralization.

Upgrades made directly to an L1, such as sharding, splitting the network into parallel segments that each process a portion of transactions, aim to raise base-layer capacity without leaving the main protocol. This differs from Layer 2 scaling, which processes transactions off the main chain and later settles the results back on it.

Choosing an L1 matters for developers and users alike: it determines transaction fees, finality time, available tooling, and the security guarantees any application built on it inherits. A chain's status as the base network, sometimes called its mainnet, makes it the ultimate source of truth for balances and contract state.