Base Speeds Up Blocks Tenfold, Retiring Flashblocks

Base, the Ethereum layer-2 network developed by Coinbase, activated its Denim upgrade on Nov. 5, replacing Flashblocks previews with five full blockchain blocks per second. The change cuts the block interval from two seconds to 200 milliseconds.

Apps using Flashblocks must update their integrations, while contracts using block counts as timers need review. Base has also reported periodic delays in getting transactions into blocks after activation.

Apps Must Switch From Flashblocks to Standard Block Feeds

Flashblocks previously streamed updates while a two-second block was still being built. Apps could display those previews quickly, but sometimes had to reverse them if the transactions were left out of the completed block.

Denim replaces that separate stream with complete blocks. Trading apps, wallets, and payment services can read transaction receipts, balances, and other state changes directly from those blocks through standard network interfaces.

Apps subscribing to newFlashblocks must switch to newHeads, the standard new-block feed. Requests that relied on Flashblocks’ pending state must instead use the latest completed blocks.

Indexers and data providers also have ten times as many blocks to process. Bridge tools that retrieve a fixed number of historical block hashes now cover one-tenth as much elapsed time.

Block-Based Timers Now Advance Ten Times Faster

The faster cadence changes how contracts interpret elapsed time. A cooldown set to 100 blocks now represents about 20 seconds, down from roughly three minutes and 20 seconds.

That affects contracts defining withdrawal delays, vesting schedules, reward periods or governance votes in blocks. Limits that reset with each new block also reset ten times more frequently.

Base recommends using clock-based timestamps for durations where contracts can be upgraded or adjusting configurable block counts to preserve the intended wait. Constants locked into contracts that cannot be upgraded may require a migration.

Denim also introduces BaseTime, which gives contracts millisecond-level timing for tasks such as expiring orders or calculating interest. The existing block timestamp value still advances in whole seconds, so several consecutive blocks can share it.

Ethereum Finality Still Comes After Base Block Inclusion

For lending and trading applications, five blocks per second create more frequent opportunities to respond to price changes, execute liquidations and update positions.

However, a transaction appearing in a 200-millisecond Base block has not yet reached Ethereum-backed finality. Its batch must first be posted to Ethereum, making it safe under Base’s terminology, and then finalized by Ethereum.

Apps can therefore show users that a transaction has entered a Base block while continuing to track whether it has reached the stronger safe or finalized stages.

Base Still Investigates Periodic Transaction-Inclusion Delays

Base confirmed successful activation at 18:14 UTC on Nov. 5, after the upgrade window began at 18:00 UTC. The same update reported periodic transaction-inclusion delays and a higher-than-expected number of empty blocks.

At 12:01 UTC on Nov. 6, that investigation remained open in Base’s upgrade-status update. Its mainnet transaction pool was marked as experiencing degraded performance, while block production, deposits, and withdrawals remained operational.