Base deploys Denim upgrade on mainnet, replacing Flashblocks with 200ms block times

Base's fourth mainnet upgrade, Denim, is live, with the Coinbase-incubated Layer 2 now producing a full canonical block every 200 milliseconds, or five per second, the project said in a statement shared with The Block on Thursday.

The upgrade also introduces millisecond-resolution timestamps for smart contracts, alongside new transfer protections and compliance controls for tokens using Base's B20 standard.

Base said the upgrade retires Flashblocks and changes how the pending block tag works, making block production "simpler, more consistent, and more reliable." Each block now follows its parent exactly 200 milliseconds later, with the protocol enforcing the interval rather than relying on the sequencer's clock. 

Applications that previously relied on Flashblocks must migrate to standard canonical block subscriptions, according to the statement.

"Base’s north star is to bring the world onchain, starting with trading, financing, and payments," the statement read. "Those use cases need a chain that updates state often and lets builders reason about time precisely."

BaseTime and B20 tokens 

According to the statement, the upgrade also introduces BaseTime, which gives smart contracts access to Unix timestamps in milliseconds. Ethereum-compatible block.timestamp remains unchanged at whole-second resolution, while new RPC fields provide millisecond timestamps for blocks, transactions, and logs.

Denim also introduces reusable compliance policies through a NOT operator and extends transfer-executor restrictions to direct transfers. It also blocks transfers, mints and seizures that send tokens to the token contract's own address, Base said.

The upgrade follows Azul, Beryl and Cobalt, Base's first three independent upgrades since its 2023 launch. Azul introduced a new client stack and multiproof system, while Beryl brought the B20 token standard. Cobalt added conditional transactions and expanded B20 compliance features.