Base’s Denim upgrade is live on mainnet, replacing Flashblocks with full canonical blocks every 200 milliseconds, or five blocks per second, according to a statement the project shared with The Block on November 5, 2026.
The upgrade is the Coinbase-incubated Ethereum Layer 2’s fourth independent network upgrade, following Azul, Beryl and Cobalt, all implemented in 2026. It also introduces millisecond timestamps for smart contracts and additional transfer protections and compliance controls for tokens using Base’s B20 standard.
Block production and application migration
Under Denim, each block follows its parent exactly 200 milliseconds later. Base said the protocol enforces that interval rather than relying on the sequencer’s clock.
The upgrade retires Flashblocks and changes the behavior of the pending block tag. Applications that relied on Flashblocks must migrate to standard canonical block subscriptions, according to the statement. Base described the resulting block-production model as “simpler, more consistent, and more reliable.”
Base framed more frequent state updates and precise timekeeping as requirements for its focus on trading, financing and payments.
BaseTime adds precision without changing block.timestamp
Denim introduces BaseTime, giving smart contracts access to Unix timestamps in milliseconds. The Ethereum-compatible block.timestamp remains unchanged at whole-second resolution.
New RPC fields also provide millisecond timestamps for blocks, transactions and logs. The distinction matters for compatibility: the existing timestamp retains its resolution, while the new functionality exposes finer-grained timing information.
B20 transfer and compliance changes
For B20 tokens, Denim introduces reusable compliance policies through a NOT operator and extends transfer-executor restrictions to direct transfers.
Base also said the upgrade blocks transfers, mints and seizures that would send tokens to the token contract’s own address.
Place in Base’s upgrade sequence
Denim follows Base’s first three independent upgrades since its 2023 launch:
- Azul introduced a new client stack and multiproof system.
- Beryl introduced the B20 token standard.
- Cobalt added conditional transactions and expanded B20 compliance features.
Denim is reported as an activated Base mainnet upgrade, not a pending proposal or an Ethereum mainnet change.
Original source: The Block. Published November 6, 2026, at 04:00 UTC+08:00 (November 5, 2026, at 20:00 UTC).