Denim Upgrade Mainnet: 200ms Native Blocks
Base (BASE) · Releases & Updates · November 2026
Base, Coinbase's OP Stack L2, targets November 2026 for the Denim mainnet upgrade that makes 200ms native blocks canonical and retires Flashblocks.
Base is the Ethereum Layer 2 network incubated by Coinbase and built on the Optimism OP Stack. Its next network upgrade, Denim, introduces native blocks at a 200ms cadence, replacing Flashblocks preconfirmations with real canonical 200ms blocks and block/RPC streams. According to the official Base upgrades page, Denim targets Base Sepolia testnet activation in October 2026 and Base Mainnet in November 2026; no activation timestamp is set yet, so the date is an estimate and may move. Denim follows the Cobalt upgrade (mainnet September 30, 2026) and Beryl (June 2026). Key topics: Base Denim upgrade, 200ms block time, Flashblocks, Base L2 latency, OP Stack hard fork, Base mainnet upgrade November 2026.