By Ali Ikhwan 
Zcash has officially activated its highly anticipated NU7 network upgrade on the testnet, marking a major milestone that transitions planned protocol changes into a live, operational testing environment roughly a month before its targeted mainnet deployment.
According to data from the Zcash testnet block explorer ZecBlock, block 4,465,026—which served as the scheduled activation point for the NU7 upgrade—was successfully mined on October 4 at 18:21:45 UTC. The official Zcash team quickly confirmed the successful activation shortly after via a post on social media platform X, assuring the developer and user community that NU7 was officially live on the testnet and operating as intended.
The NU7 upgrade represents the next major network evolution for Zcash, introducing a series of aggressive protocol changes designed to optimize transaction throughput, improve network economics, and sunset legacy transaction formats. Among the most prominent adjustments included in NU7 is a dramatic reduction in the network’s target block spacing. While previous iterations of Zcash operated on a 75-second block time, the NU7 upgrade slashes this target down to just 25 seconds. This threefold acceleration in block generation is expected to significantly speed up confirmation times for users, providing a more responsive and fluid transaction experience.
In addition to faster blocks, the NU7 upgrade introduces several critical structural changes to the Zcash protocol. These include disabling version 4 transactions entirely and integrating a new economic model known as the Network Sustainability Mechanism. This innovative mechanism is designed to redirect a specific portion of transaction fees back into future block rewards, creating a more sustainable long-term economic foundation for the network’s validators and ecosystem participants.
However, the phasing out of version 4 transactions carries significant implications for users holding funds in older, legacy structures within the ecosystem. Specifically, disabling version 4 transactions means that any ZEC currently held in Zcash’s legacy Sprout shielded pool will become entirely unspendable unless users take proactive measures to move their funds out of the legacy pool before the NU7 upgrade reaches full activation on the mainnet. This transition underscores the ongoing technical evolution of privacy-preserving cryptographic networks, as older architectures are phased out in favor of more modern, efficient cryptographic frameworks.
Following the successful testnet deployment, the Zcash Foundation issued a statement encouraging network operators, developers, and node runners to utilize the release candidate to test NU7 under real-world conditions. The Foundation emphasized that this crucial testnet phase allows developers to thoroughly assess the performance, stability, and security of the upgrade before committing to a final decision regarding mainnet activation.
The evaluation period on the testnet is a standard yet vital procedure in major protocol upgrades, providing a controlled sandbox environment to catch unforeseen bugs or operational friction. Zcash developers are scheduled to convene on October 20 to review the performance data gathered from the testnet trial. During this meeting, developers will make a final, formal decision on whether to proceed with mainnet activation and will set the exact activation block height. If the testnet phase continues to progress smoothly without major roadblocks, the mainnet activation for the NU7 upgrade is targeted for November 5.
Nana Wu