Genesis and Block 0

Genesis is the one-time process of starting a new chain and producing its first block.

What happens at genesis

1. The sequencer starts with an empty database.
2. It loads a hardcoded file (genesis.json) that defines the initial on-chain state.
3. This file deploys exactly three system contracts:
   • GenesisUpgrade
   • L2WrappedBase
   • ForceDeployer
4. After loading these, the sequencer begins listening to L1 events that describe the first actual L2 block:
   • Bytecodes to deploy additional contracts (ForceDeployer enables this)
   • Parameters passed to GenesisUpgrade to finish remaining initialization steps

Why these contracts exist

• ForceDeployer: Allows forced deployment of predefined contract bytecode needed at boot.
• GenesisUpgrade: Finalizes system configuration after initial contract deployment.
• L2WrappedBase: Provides a required base implementation (infrastructure dependency).

Security perspective

L1 already knows the exact expected initial L2 state (the three contracts and their storage layout).
This state is defined in zksync-era’s genesis.json and is consumed by the zkStack tooling when setting up the ecosystem on L1.
Because L1 has this canonical reference, it can validate that the L2 started correctly.

Summary

Genesis = load predefined state from genesis.json -> deploy 3 core contracts -> process L1 events to finalize initialization -> produce block 0.