By Nana Wu 
Zcash has officially advanced its roadmap by activating its highly anticipated NU7 network upgrade on the testnet, successfully transitioning the planned protocol modifications into a live testing environment approximately one month ahead of its targeted mainnet rollout.
According to data from the Zcash testnet block explorer ZecBlock, block 4,465,026—which served as the predetermined activation point for the NU7 upgrade—was successfully mined on Oct. 4 at 18:21:45 UTC. Shortly after the milestone was reached on the decentralized network, Zcash confirmed the successful deployment in an official public statement shared via a post on social media platform X, assuring the broader cryptocurrency community that NU7 is now officially live on the testnet.
The deployment of NU7 represents a significant structural evolution for Zcash, marking its next major network upgrade. Among its most prominent features, the upgrade seeks to drastically reduce the network’s target block spacing from the current 75 seconds down to a much faster 25 seconds. This reduction in block time is designed to improve the overall responsiveness and throughput of the network, offering a more streamlined experience for users engaging with the protocol.
In addition to accelerating block times, the comprehensive NU7 upgrade introduces several critical adjustments to the network’s underlying architecture and economic model. Most notably, the upgrade disables version 4 transactions and integrates a newly designed Network Sustainability Mechanism. This mechanism is engineered to redirect a portion of transaction fees back into future block rewards, establishing a sustainable funding loop to support the ongoing security and maintenance of the network over the long term.
However, the deprecation of version 4 transactions carries significant practical implications for asset holders. The disabling of these legacy transactions means that any Zcash (ZEC) still held within the network’s legacy Sprout shielded pool will become entirely unspendable. To prevent permanent loss of access or locked capital, users holding funds in these legacy pools have been strongly advised to migrate their assets out of the Sprout pool before NU7 fully activates on the mainnet.
Ahead of the testnet milestone, the Zcash Foundation released a statement on Friday encouraging independent testnet operators and node runners to utilize the newly available release candidate to test NU7 under real-world conditions. This crucial testing phase provides developers, validators, and ecosystem participants with a vital window to assess the stability, performance, and security of the upgrade before any final decisions are made regarding a mainnet rollout.
The ongoing testnet evaluation period is a standard yet essential step in Zcash’s rigorous governance and deployment pipeline. Developers are scheduled to reconvene on Oct. 20 to review performance data and telemetry gathered during the testnet phase. Based on these findings, they will make a final, formal decision on whether to proceed with mainnet activation and establish the precise activation block height. If the testnet evaluation continues to proceed according to schedule, the official mainnet activation for NU7 is currently targeted for Nov. 5.
Ali Ikhwan