Layer 1

A layer 1 is a base blockchain that handles its own consensus, security, and data — the foundation network on which everything else settles. Bitcoin, Ethereum, Solana, and Avalanche are all layer 1s: each has its own validators or miners, its own native coin used to pay fees, and its own rules, and none depends on another chain to finalize its transactions.

The term exists mostly in contrast to layer 2, the networks built on top of a layer 1 to process transactions more cheaply while inheriting its security. In that stack, the layer 1 is the court of final settlement: a rollup like Arbitrum executes thousands of transactions off-chain but ultimately posts its data and proofs to Ethereum, so disputes and withdrawals are resolved by Ethereum's consensus. For example, when Ethereum fees spike, users may transact on a layer 2 instead, but the assets they move remain anchored to Ethereum, the layer 1.

Layer 1 design is where the famous scalability trilemma bites: it is hard to maximize decentralization, security, and throughput simultaneously, so base chains make different trade-offs — Bitcoin prioritizes simplicity and security, Solana pursues raw throughput with heavier hardware requirements, Ethereum increasingly positions itself as a secure settlement and data layer while pushing scale to layer 2s. A common misconception is that "layer 1" implies superiority over layer 2; the layers are complementary roles in a stack, not a quality ranking, and much everyday activity now deliberately happens off the base layer.