Builders maintaining Base applications that relied on Flashblocks must migrate to standard canonical block subscriptions, according to a Base statement reported by The Block. The network’s Denim mainnet upgrade retires Flashblocks and introduces full canonical blocks every 200 milliseconds—five per second.
The original report was published on November 6, 2026, at 04:00 UTC+8. It described Denim as Base’s fourth independent network upgrade, following Azul, Beryl and Cobalt in 2026.
Block production and subscriptions
Base, the Coinbase-incubated Ethereum Layer 2 network, said Denim makes block production “simpler, more consistent, and more reliable.” Each canonical block now follows its parent exactly 200 milliseconds later. The protocol enforces that interval rather than relying on the sequencer’s clock.
The upgrade also changes how the pending block tag works. The supplied report does not detail its revised behavior, but explicitly identifies migration from Flashblocks to standard canonical block subscriptions as a requirement for applications that used Flashblocks.
Millisecond time without changing block.timestamp
Denim introduces BaseTime, which gives smart contracts access to Unix timestamps in milliseconds. This is distinct from the Ethereum-compatible block.timestamp, which remains at whole-second resolution.
New remote procedure call (RPC) fields also provide millisecond timestamps for blocks, transactions and logs. For builders, the important distinction is that the upgrade adds finer-grained time access; it does not change the resolution of the existing block.timestamp value.
Base linked these changes to its focus on trading, financing and payments, saying those uses require frequent state updates and precise reasoning about time.
B20 token transfer and compliance changes
For tokens using Base’s B20 standard, Denim adds or extends several controls, according to Base:
- Reusable compliance policies through a
NOToperator. - Transfer-executor restrictions that now extend to direct transfers.
- Protection against transfers, mints and seizures that would send tokens to the token contract’s own address.
Where Denim fits
Base launched in 2023. Its first three independent upgrades introduced different parts of the network’s tooling and token functionality: Azul added a new client stack and multiproof system; Beryl introduced the B20 token standard; and Cobalt added conditional transactions and expanded B20 compliance features.
Denim’s reported changes center on block cadence, time precision and token controls. The announcement establishes those software changes, not their adoption or market impact.
Original source: The Block — “Base deploys Denim upgrade on mainnet, replacing Flashblocks with 200ms block times”, published November 6, 2026, at 04:00 UTC+8.