Zcash, a privacy-focused cryptocurrency project developed by the Electric Coin Company, is preparing for a significant overhaul of its blockchain protocol with the arrival of Network Upgrade 7 (NU7), scheduled for November 5. The upgrade will implement major performance improvements, most notably cutting block times from the current 75 seconds to just 25 seconds. This change is set to enhance transaction throughput and user experience.
Major Protocol Changes and New Features
Network Upgrade 7 introduces several technical advancements. Beyond reducing block creation intervals, the update will disable Sprout transactions, a legacy feature in the protocol. Zcash users who still hold ZEC in the older Sprout pool have been urged to transfer their assets to the newer Sapling pool before the update activates.
The reduction in block times builds upon previous work done in Zcash’s 2019 Blossom upgrade, which halved block intervals from 150 seconds to 75 seconds. At the same time, Blossom also shortened the migration timeframe from Sprout to Sapling pools, streamlining network operations and facilitating the shift away from earlier protocols.
The Zcash engineering team released Zebra 7.0.0 on October 22, marking the first stable mainnet-compatible version to support Network Upgrade 7. Operators running mainnet nodes are required to upgrade to Zebra 7.0.0 prior to network height 3,543,405—corresponding to the anticipated November 5 activation. Running earlier versions, such as Zebra 6.4.x, will cause nodes to halt before the upgrade is enforced, ensuring all participants remain on the consensus chain.
Mini dictionary: Zebra is a Rust-based, fully compatible alternative client for Zcash, developed to enhance network diversity, reliability, and future scalability alongside the reference zcashd implementation.
Network Sustainability and Fee Mechanisms
With NU7, Zcash introduces a Network Sustainability Mechanism, which modifies how transaction fees are distributed and advances the network’s long-term economic model. Under proposal ZIP 235, 60% of every block’s transaction fees will be removed from circulation and placed into a reserved pool, while miners receive the remaining 40% as an incentive to process transactions. ZIP 237 outlines a plan in which blocks will later reissue a small, predictable portion of that reserve as additional rewards, starting at mainnet height 8,939,664 under ZIP 259. The overall coin supply cap of 21 million ZEC and the established four-year halving schedule remain unchanged.
Zcash’s NU7 upgrade moves to 25 second block intervals, adds a mechanism to recycle part of every transaction fee into future block rewards, and puts new per-block transaction limits in place to boost throughput and keep wallets safe from spam attacks. The total ZEC supply and halving cycle are unaffected by these changes.
Enhanced Network Security and Spam Protection
The NU7 release is also set to fix seven previously identified security issues while improving synchronization speeds for nodes close to the blockchain tip. Per-block limitations will apply to Orchard, Ironwood, and Sapling activities, but Sprout JoinSplits will be discontinued to phase out the outdated protocol layer.
NU7, through ZIP 218, brings a dramatic improvement to both transaction speed and resistance to network spam. The limit adjustments are expected to more than double throughput in the Orchard shielded pool, raising potential transactions per second from 2.9 to 6.6. At the same time, worst-case bandwidth usage that malicious actors could direct at lightweight wallets is projected to drop by approximately 37%.
| Feature | Before NU7 | After NU7 |
|---|---|---|
| Block Time | 75 seconds | 25 seconds |
| Orchard Throughput | 2.9 tps | 6.6 tps |
| Worst-case Sync Bandwidth (Wallets) | Higher | 37% lower |
| Transaction Fee Allocation | 100% to miners | 40% to miners, 60% to reserve |
| Sprout Transactions | Enabled | Disabled |
These network-wide updates aim to modernize Zcash’s transaction processing capacity while reinforcing protections against spam and ensuring a sustainable, long-term path for miner incentives as block rewards gradually decrease with each halving event.
