Base’s Denim upgrade cuts block times to 200ms, with mainnet targeted for November

“Coming soon to Base mainnet”

Base kept it short on 23 October: “200ms blocks. Coming soon to Base mainnet.” The change arrives with Denim, the network’s next upgrade. Base’s documentation shows Denim live on the Base Sepolia testnet since 21 October and mainnet in planning for November 2026.

Base stresses that November is a planning target, not an activation time, and may change. The node software versions needed for mainnet had not been published when Exchange.news read the documentation.

Five blocks a second

Today Base produces one block every two seconds. Denim switches to five complete blocks a second, each with its own block number, hash, state root and receipts. In our reading, apps on Base should be able to confirm activity faster; Base itself has not published user-facing latency figures beyond the block cadence.

Denim also retires Flashblocks, the stream of partial in-block updates Base uses today for fast pre-confirmations. Base will stop producing them during the rollout, so apps that rely on Flashblocks must move to regular block and RPC streams. Denim also brings B20 transfer and policy changes for token issuers.

What developers should check

The main catch is time measured in blocks. Because block numbers will advance ten times faster while block timestamps still move in whole seconds, any timelock, cooldown, vesting schedule, deadline or governance voting period counted in blocks will run out ten times sooner after activation. Base advises switching to timestamp checks where contracts can be upgraded, dividing governance-tunable block counts by ten at activation and planning a migration for immutable contracts. Logic based on timestamps is unaffected.

For sub-second precision, Denim adds BaseTime, a system contract exposing each block’s millisecond component, and optional millisecond timestamp fields in RPC responses. The existing seconds-based fields stay as they are.

After Cobalt

Denim follows Cobalt, which Base’s engineering team brought to mainnet on 30 September. Cobalt added Validity Transactions, which sit dormant until conditions set by the user are met, and enhancements to Base’s B20 token standard. The Cobalt announcement already named 200ms blocks as the next step and said they would keep the same reorg guarantees as today’s two-second blocks. The artwork above is from that Cobalt announcement.