Base Makes a Block Every 200 Milliseconds and Retires Flashblocks

Base produced its first 200-millisecond block on Thursday, and the two-second block it had run since launch is gone. The Denim upgrade makes a full canonical block five times a second and enforces the interval in the protocol, instead of leaving the timing to the sequencer's clock. It also retires Flashblocks, the preconfirmation stream Base built with Flashbots and ran from July 2025. Applications that read Flashblocks have to move to standard block and remote procedure call subscriptions. Anything on the chain that counts blocks instead of seconds now runs out ten times faster.

What the old block looked like

Flashblocks pushed partial results out every 200 milliseconds as each two-second block filled, and applications could treat those as preconfirmations, meaning early and revocable views of what the block would hold. Denim promotes each of those pieces to a block in its own right. The interval did not change. The thing arriving at it did. Three accounts give the old block time as two seconds: Unchained, Altcoin Buzz and The Industry Spread, the last of which set out the mechanics two weeks before mainnet. The Block's story on the upgrade never states the old figure at all, so the size of the change goes unstated in the account most readers will meet first. The pending block tag has no direct equivalent now either.

The clock, and who checked it

Unchained put activation at 18:00 UTC and said it read the network's public data, naming block No. 53,556,127 at 18:00:01 UTC as the first at the new cadence. Altcoin Buzz gives the same time and says plainly that it could not confirm it: the documentation still read "planning" when it looked, and no on-chain check was open to it. The Block gives no activation time. One outlet verified the clock and one said it could not. Base's own status page called the upgrade successfully activated about a quarter of an hour in, on Unchained's account.

"Base's north star is to bring the world onchain, starting with trading, financing, and payments," the statement read. "Those use cases need a chain that updates state often and lets builders reason about time precisely."

Ten times faster is not only about speed

Block numbers now advance ten times faster against the wall clock, and every contract that measures time in blocks inherits that. A one-hour cooldown written as 1,800 blocks lapses in about six minutes. A week-long timelock of 302,400 blocks expires in under 17 hours. Both of those come from single accounts and are arithmetic, not observation, though the direction is not in dispute. Denim also adds BaseTime, which hands contracts Unix timestamps in milliseconds while the Ethereum-compatible block.timestamp stays at whole seconds and new data fields carry the finer value. On the token side, transfers, mints and seizures that would credit a token contract's own address now revert, transfer-executor restrictions reach direct transfers, and any compliance policy can be inverted. Those controls extend the rules Cobalt introduced, which in turn sat on the B20 standard Beryl shipped.

What Denim does not carry

Native transaction batching and gas sponsorship are absent from this upgrade. They belong to Everest, which has no activation date in either account that mentions it. Denim is the fourth upgrade Base has shipped on its own, after Azul, Beryl and Cobalt, all three of them this year. The Block calls that series independent network upgrades, Altcoin Buzz calls them major ones, and a third account gives no count at all. One outlet dates each of the three to a month and the others give no months, so those dates do not reconcile and are left out here. The first minutes of the faster chain were thin: on Unchained's count 146 of the first 300 blocks carried only system transactions, while hourly samples later that afternoon had none. That is one outlet's reading of a few minutes of chain, and nobody else has published a second count.