Base deployed its Denim mainnet upgrade, replacing Flashblocks with full canonical blocks produced every 200 milliseconds, or five per second, according to a project statement shared with The Block on Thursday, November 5, 2026.
Denim is the Coinbase-incubated Layer 2’s fourth independent network upgrade. Alongside the block-production change, it introduces millisecond timestamps for smart contracts and additional transfer protections and compliance controls for tokens using Base’s B20 standard.
What changes for block production
Under Denim, each block follows its parent exactly 200 milliseconds later. The protocol enforces that interval rather than relying on the sequencer’s clock.
Base said the upgrade retires Flashblocks and changes the behavior of the pending block tag, making block production “simpler, more consistent, and more reliable.” Applications that relied on Flashblocks must migrate to standard canonical block subscriptions, according to the statement.
Base linked the changes to its focus on trading, financing and payments, saying those uses require frequent state updates and precise handling of time.
Millisecond timing without changing block.timestamp
Denim introduces BaseTime, which gives smart contracts access to Unix timestamps in milliseconds. The Ethereum-compatible block.timestamp remains unchanged, with whole-second resolution.
New RPC fields also provide millisecond timestamps for blocks, transactions and logs. The distinction matters for developers: the upgrade adds finer-grained timing access without changing the resolution of the existing block.timestamp value.
Additional B20 transfer controls
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.
Where Denim fits in Base’s upgrade history
Denim follows Azul, Beryl and Cobalt, all implemented in 2026. These were 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.
Original publication time: November 6, 2026, at 04:00 UTC+8 (November 5 at 20:00 UTC).