Definition
Layer 1 (L1) refers to a base blockchain network rather than an application or scaling system built above it. Bitcoin and Ethereum are common examples. An L1 maintains its own accepted state or history through protocol-defined validation and consensus. The label describes its architectural role, not its speed or relative quality.
Relationship with Other Layers
Applications can execute directly on a suitable L1, while additional systems may perform activity elsewhere and use it for settlement, data publication or security. An Ethereum rollup, for example, interacts with Ethereum under its design’s verification and data rules. A separate chain connected by a bridge does not automatically inherit the base chain’s security.
Key Considerations
L1 designs balance factors such as verification costs, capacity, resilience and decentralization. Increasing block capacity is not a cost-free improvement because it can raise resource requirements. Fees and finality differ across networks. When assessing an application, identify which guarantees come from the L1 and which depend on contracts, sequencers, bridges or other operators. Layer labels alone do not describe every dependency.