Zcash Activates NU7 Upgrade, Aiming for 25-Second Blocks and Faster Private Payments

Faster confirmations, with service-dependent wait times

Zcash is built to let users send funds without revealing the sender, recipient or amount. With NU7 live, a payment’s first confirmation can now arrive in roughly 25 seconds on average, which could make shielded transfers more practical for retail payments, exchange deposits and cross-chain fund movements.

The effect on actual user wait times will still depend on the policies of the service receiving the payment. A merchant that accepts a single confirmation could see that first signal in about 25 seconds, while an exchange that asks for three confirmations could reduce the expected wait from nearly four minutes to around 75 seconds.

Early block production showed the network still adjusting

The faster pace was not immediate in the first hours after activation. By 04:59 UTC, Zcash had produced 225 additional blocks after the upgrade, with an average spacing of about 39 seconds, according to ZecStats.

That gap from the new 25-second target reflected mining difficulty still adjusting. Difficulty determines how hard it is to produce a block, and it takes time for that setting to adapt when a network changes its intended block cadence.

Why shorter block times required broader technical changes

Reducing the interval between blocks involves more than changing a timing parameter. After one miner finds a block, the rest of the network needs time to receive and verify it before moving on. With shorter intervals, there is less margin for other miners to catch up, increasing the chance that competing blocks are created and later discarded.

Zakura, the Zcash node software developed by Valar Group and Project Tachyon, was tested on 80 computers across 11 regions with every block filled with transactions. Under those conditions, 3.43% of mined blocks were discarded, compared with 1.57% under the previous 75-second schedule.

Engineers also worked to reduce repeated verification work. The software checks a transaction when it first arrives and keeps part of that result, so it does not need to repeat every step from the beginning when the same transaction later appears in a block. Checks tied to current balances and blockchain history still have to run again.

Wallet load, capacity and fee distribution also changed

NU7 places a cap on how much private transaction activity can fit into each block. That matters because wallets must scan the chain to detect payments intended for them, and a flood of private transactions can force every wallet to perform more work.

According to the upgrade specification, the new limits reduce the worst-case daily download burden from 271 megabytes to 169. Combined with more frequent blocks, the same specification estimates that capacity for simple private payments could rise from about three transactions per second to more than six.

Transaction fees are now split differently as well. Miners receive 40% of fees, while the remaining 60% is removed from circulation and tracked in a reserve that is set to begin supplementing future block rewards around February 2031. The mechanism is intended to preserve Zcash’s 21 million coin supply cap.

Sprout has been retired, with one recovery idea still unapproved

NU7 also retires Sprout, Zcash’s original privacy pool introduced in 2016. As a result, about 12,224 ZEC has become unspendable.

Zcash co-founder Sean Bowe has outlined a possible way to recover those funds, but no such mechanism had been approved as of Friday. The next confirmed step is the network’s continued transition toward the new block schedule as mining difficulty adjusts to the faster target.