A Layer 1 blockchain is the base blockchain protocol that maintains its own consensus, ledger state, transaction ordering, and native settlement rules.
Layer 1 networks define the core execution and consensus environment for transactions and smart contracts. Their validators or block producers determine the authoritative ledger according to the protocol. Scaling changes made directly to the base protocol, such as block-capacity or consensus improvements, occur at Layer 1. Stablecoins issued natively on several Layer 1 networks can create separate issuer-recognized token supplies on each network.
Layer 1 is the base consensus and settlement layer. Layer 2 protocols process some activity outside or above the base layer while relying on Layer 1 to varying degrees for settlement, security, data availability, or dispute resolution.
Layer 1 design determines the underlying security, fee market, transaction capacity, and finality inherited by stablecoin activity on that network.
Ethereum is a Layer 1 blockchain on which stablecoins can be issued directly as smart-contract tokens.