Base schedules Denim for November 5 at 19:00 Paris time, with 200-millisecond native blocks

A scheduled activation and an announced maintenance window

Base plans to activate Denim on mainnet on November 5 at 18:00 UTC, or 19:00 in Paris. Its official status page lists a maintenance window ending at 20:00 UTC, or 21:00 in Paris, and says the network is expected to remain operational during that period. At the time of this morning’s check, the documentation still describes the mainnet deployment as planned. The announced time must therefore be distinguished from an activation that has actually been observed.

Denim has been running on the Sepolia test network since October 21. For mainnet, Base asks node operators to upgrade to version 1.5.1 before activation. The maintenance notice also warns operators of older installations to remove an experimental validity-transaction option from their startup command if it is still present. Otherwise, the affected node may fail to start. These instructions concern infrastructure operators, rather than an action every user needs to perform in a wallet.

Native blocks replace Flashblocks

The central change concerns block production: Denim is designed to produce a complete canonical block every 200 milliseconds, compared with one every two seconds previously. Each block is to have its own hash, state and receipts. Base thus describes a move to five complete blocks per second. This cadence refers to the network’s block production; it does not measure guaranteed transaction capacity or the final settlement time of a transfer to another blockchain.

Denim replaces Flashblocks. Applications consuming those streams need to migrate to canonical block streams and the corresponding interfaces. For developers, the issue therefore goes beyond a simple speed improvement: monitoring, display and processing systems must understand the finer granularity. The migration documentation and release notes remain the references to consult before changing a service used by customers.

Timekeeping and token rules also change

A component called BaseTime provides onchain time information at millisecond resolution. The Ethereum Virtual Machine’s usual timestamp field remains seconds-based to preserve compatibility. Some RPC interface responses gain optional millisecond fields. The upgrade also tightens certain B20 rules: transfers to the token’s own address must fail, and executor policies apply across transfer paths. These changes may require specific adjustments in affected applications.

The useful evidence after 19:00 will be observed activation, followed by the operation of updated nodes and integrations. A maintenance announcement does not guarantee an incident-free process, even when the network is expected to remain accessible. The schedule here rests on a notice published on October 30 and version 1.5.1 release notes published on October 22: the November 5 news is their operational deadline, rather than a new announcement issued today.