Zcash developers propose 20-second blocks days after major upgrade

Zcash developers have proposed reducing the network’s block time from 25 seconds to 20 seconds, just days after the NU7 upgrade made transaction confirmations three times faster.

According to a proposal published on the Zcash community forum on Nov. 8, developers Dev Ojha, known as ValarDragon, and Evan Forbes want the change considered for the upcoming NU7.1 upgrade. Their proposal follows early network results showing that faster blocks have not caused the increase in competing blocks that developers initially feared.

The proposed adjustment would reduce the expected time for a transaction’s first confirmation by another five seconds. However, the developers have not received community approval, and there is no confirmed activation date.

Zcash developers seek faster blocks after NU7 upgrade

Zcash activated its NU7 upgrade on Nov. 6 at block 3,543,405, reducing the target time between blocks from 75 seconds to 25 seconds. The update changed how quickly miners add transactions to the blockchain without changing the cryptocurrency’s maximum supply.

As crypto.news previously reported, NU7 introduced new shielded transaction limits and a system that reserves 60% of transaction fees for future mining rewards. Miners receive the remaining 40% directly.

With the network now producing blocks three times more frequently, developers are considering another reduction to improve the time users spend waiting for payments to be confirmed.

Under the latest proposal, a transaction requiring one confirmation would have an expected wait of approximately 20 seconds, compared with 25 seconds under the current rules. For an exchange requiring three confirmations, the target waiting period would fall from 75 seconds to 60 seconds.

Actual confirmation times can vary because miners do not discover blocks at fixed intervals. Exchanges and other service providers can also set their own confirmation requirements before making deposited funds available.

The developers identified retail payments, exchange deposits and cross-chain swaps as activities that could benefit from the shorter interval. The change would be particularly relevant for transactions that require blockchain confirmation before another service can process them.

Early mining results support proposed 20-second blocks

A central concern surrounding faster blocks is the possibility of more orphaned blocks, which occur when miners produce competing blocks before the network reaches agreement on which one to accept.

Only one competing block becomes part of the accepted chain, leaving miners responsible for discarded blocks without rewards for that work. Reducing the time between blocks can make such conflicts more frequent.

However, early data from ZecBlock’s mining tracker showed an observed orphan rate of 0.69% over the 24 hours ending early Monday, compared with approximately 0.66% before NU7.

The rate measured across the entire period following the upgrade was higher at 1.29%, reflecting an initial rise before subsequent readings declined.

“The orphan rate has gotten better than I anticipated!” Ojha (@zkDragon) wrote in a Monday update.

The monitoring service expanded its observation network from one node to ten shortly before the upgrade. Because the additional nodes can detect competing blocks that previously went unrecorded, the earlier and current figures are not directly comparable.

Developers conducted separate tests using 80 miners distributed across 12 geographic regions to examine how the proposed 20-second interval would perform under demanding network conditions.

The simulations produced orphan rates ranging from 1.9% to 3.3%, depending on the mining software configuration. Earlier tests used to assess the safety of 25-second blocks recorded an orphan rate of 4.68%.

Proposed Zcash changes would preserve transaction capacity

Although the proposal would produce blocks more frequently, developers do not intend to raise the number of private transactions the network can process each day.

The draft technical plan would reduce the maximum number of shielded actions permitted in each block from 330 to 264. The 2 MB block size limit would remain unchanged.

Developers explained that maintaining the current per-block limits while creating more blocks would increase the amount of data wallets might need to download and process.

The proposal would also adjust the block subsidy and halving interval to preserve Zcash’s existing issuance schedule and its maximum supply of 21 million ZEC.

Another proposed change concerns difficulty adjustment, which determines how difficult miners find it to produce new blocks.

In a Nov. 9 post, Ojha explained that NU7 increased the difficulty averaging window from 17 blocks to 102 blocks. The proposed 20-second interval would raise that figure to 128 blocks.

He estimated that difficulty fluctuations previously ranging from approximately -40% to +30% could narrow to between -20% and +15%, although actual network performance remains to be observed.

Developers seek community approval for NU7.1

Ojha and Forbes want the proposal included in the next Zcash community poll and considered for NU7.1, a follow-up network upgrade.

The developers have not announced an activation schedule or secured approval to change the block interval.

Meanwhile, the earlier NU7 implementation required node operators to update their software to remain compatible with the network’s new consensus rules.

The latest proposal would retain the recommended confirmation anchor depth of three blocks, reducing its expected duration from 75 seconds to 60 seconds. It would also increase the default transaction expiry from 120 blocks to 150 blocks, preserving the same expected expiry period despite faster block production.