Zcash developers have introduced a proposal aiming to reduce the network’s block interval from 25 seconds to 20 seconds, following the recent activation of the NU7 network upgrade. The plan, set forth by Zcash contributors Ojha and Forbes on November 8, requests that community members consider this modification during the next scheduled governance vote. Although still in its draft stage, the initiative could shorten waiting times for payments across the privacy-focused blockchain network.
Recent Upgrades and Proposed Changes
Zcash, a blockchain designed to offer confidential transactions, launched the NU7 update at block 3,543,405 on November 6. The upgrade significantly accelerated transaction confirmations by reducing the target block interval from 75 seconds to 25 seconds. Other features in NU7 included raising the cap on shielded transaction limits and earmarking 60% of future mining rewards for designated reward pools.
If the block time is further reduced to 20 seconds as proposed, users could see confirmation times shrink from 75 seconds down to one minute when three confirmations are required. This adjustment could benefit retail payments, deposits on exchanges, and cross-chain swaps by providing faster and more predictable completion times.
Zcash developers have explained that a shortened block interval could boost transaction speed without altering coin issuance, but it requires careful evaluation to balance network security and efficiency.
Developers emphasize, however, that this proposal serves as an intermediary step and not the ultimate block speed target. Discussions are underway to determine whether further reductions could occur without disrupting mining activity across the network.
Potential Tradeoffs: Orphan Blocks and Network Security
Block time acceleration may increase the chance of competing block discoveries, where two miners generate blocks at nearly the same moment. The protocol selects one to continue the main chain, while the other is orphaned, leading to lost rewards for the affected miner.
Early findings from ZecBlock monitoring show Zcash’s orphan block rate stood at 0.69% in the 24-hour period after the NU7 upgrade, compared to 0.66% beforehand. The average since NU7’s activation has been 1.29%. Developers point out that improvements to the monitoring infrastructure, which now aggregates data from ten network nodes instead of one, may account for the rise and caution that the current observation period is too short for definitive conclusions.
Simulations run by developers suggest that with a 20-second block interval and 80 miners across 12 global regions, orphan block rates would reach 1.9% when using Zakura nodes and 3.3% with mixed software, compared to 4.68% for 25-second intervals in earlier tests.
These results fit within Zcash’s developer-defined safety margins, yet teams caution that simulations may not perfectly predict real-world mainnet behavior and plan to continue monitoring the situation closely.
Mini dictionary: ZecBlock, an independent monitoring project, aggregates real-time network data for Zcash, including orphan block rates and other performance indicators.
| Period | Block Time Setting | Orphan Block Rate |
|---|---|---|
| Before NU7 (75s block) | 75 seconds | 0.66% |
| After NU7 (25s block) | 25 seconds | 0.69% |
| Simulation (25s block) | 25 seconds | 4.68% |
| Simulation (20s block, Zakura nodes) | 20 seconds | 1.9% |
| Simulation (20s block, mixed software) | 20 seconds | 3.3% |
Maintaining Privacy and Capacity
To balance the accelerated block rate with network privacy features, the proposal reduces the maximum shielded actions per block from 330 to 264. For the Sapling protocol, input-output limits would fall from 300 to 240 transactions. The overall block size limit remains at 2 MB, and no changes to the long-term coin supply are planned as the 21 million cap is maintained.
With more frequent block creation, daily private transaction capacity could rise. Zcash’s developers intend for speed improvements to occur without inflating block throughput or increasing the frequency of wallet scanning. Adjustments to the mining difficulty window and transaction expiry defaults are also planned: the former would extend to 128 blocks and the latter to 150 blocks, aligning with the faster block issuance.
Next Steps and Community Decision-Making
A public vote among Zcash stakeholders is expected before any activation date or height is set for the 20-second block target. If approved, NU7.1 would formalize the change, keeping the network’s recommendation of a three-block anchor time, totaling 60 seconds for finalized transactions.
Until consensus is reached and the upgrade is scheduled, Zcash will continue operating with the recently adopted 25-second block interval from NU7.
