Zcash Proposal Seeks 20-Second Blocks After NU7 Upgrade

By Elena Vasquez

Zcash developers proposed cutting the network’s target block interval from 25 seconds to 20 seconds on Sunday, days after the NU7 upgrade activated on mainnet. ValarDragon and Evan Forbes submitted the draft Zcash Improvement Proposal to the community forum on Sunday. It remains unapproved and targets the next community poll and possible inclusion in NU7.1.

What does the 20-second proposal change?

The draft would build on NU7, which went live Friday and reduced the target interval from 75 seconds to 25 seconds. In the forum submission, the developers said: “The proposal, if approved, would make first confirmation, payments, exchange deposits, and cross-chain transactions faster without placing significantly greater demands on the network.”

That statement describes intended operating results, not evidence from a live deployment. The 20-second setting has not passed the community process or operated under ordinary mainnet conditions.

The proposal retains Zcash’s 2 MB block size limit while changing several related settings:

• Adjusting shielded-transaction limits to prevent light wallets from downloading and processing more data each day.
• Changing block issuance, the Network Sustainability Mechanism’s reissuance rate, difficulty averaging, and default transaction expiry.
• Adjusting other settings to preserve the network’s existing timing as block production becomes more frequent.

Keeping current limits while shortening block times could increase the daily workload for nodes and wallets by 25%, according to the developers. These adjustments are therefore workload controls, not merely confirmation-speed changes.

Unlike ZIP 218, which deployed with NU7, the new ZIP is a smaller adjustment focused on reducing delays. The practical result would be quicker first confirmations without larger blocks, provided the revised limits contain the additional daily processing burden.

What do the 20-second safety tests show?

Reducing the interval from 25 to 20 seconds gives miners less time to receive and verify new blocks. That can increase competing blocks, with one block rejected as orphaned, so the draft relies on tests of that risk.

Developers tested an 80-miner network across 12 regions. They recorded orphan rates of 1.9% when miners used Zakura alone and 3.3% when they used two implementations, Zakura and Zebra-Andele.

Those figures were close to the NU7 tests supporting the 25-second interval. The earlier tests recorded 4.68% in an experiment and 3.26% in a theoretical model. Developers’ conclusion was that Zcash can move to 20-second blocks “without major reliability problems.”

The caveat is material: the trials ran in a controlled environment, and the developers cautioned that results could differ after deployment. The tests support the proposal, but they do not establish how the live network will behave under real transaction and mining conditions.

The practical takeaway is reassuring but bounded: measured orphan rates were low in simulation, not guaranteed on mainnet.

What happens before 20-second blocks become active?

The draft must clear the next community poll and then face consideration for NU7.1, the stated implementation path. It remains a proposal, not an adopted rule, and no live 20-second schedule is in force.

Exchanges may retain their existing confirmation requirements. Faster block production therefore does not automatically reduce confirmations or weaken transaction-security policies.

At publication, ZEC traded at approximately $1.217, down 3.14% over the previous 24 hours. That market move does not change the proposal’s approval status.

The next community poll and NU7.1 review are the decision points; without approval, Zcash’s target interval remains 25 seconds.