Until now, Base produced one canonical block every two seconds and relied on Flashblocks to stream faster pending-state updates. Coinbase's Layer 2 has activated the Denim upgrade on mainnet, its fourth mainnet upgrade, after a Sepolia testnet run since October 21.

Base now produces five full canonical blocks per second, one every 200ms.

Each 200ms block has its own hash, state root and receipts. Denim also adds onchain millisecond time through a BaseTime predeploy, millisecond-resolution RPC timestamps and tighter transfer and policy rules for B20 tokens.

Denim replaces Flashblocks entirely, so applications built on Flashblocks need to migrate to the canonical block and RPC streams.