Zcash has officially advanced its upcoming protocol overhaul, deploying the NU7 network upgrade to its public testnet. This crucial milestone initiates a multi-week live testing phase, giving developers, node operators, and infrastructure providers an opportunity to thoroughly evaluate major technical changes, including a drastic reduction in block times, before a targeted mainnet rollout in November.
According to data from the Zcash testnet block explorer ZecBlock, block 4,465,026—which was hardcoded as NU7’s scheduled activation point—was successfully mined on Oct. 4 at 18:21:45 UTC. The Zcash development team quickly confirmed the milestone to the broader community, taking to social media platform X to announce that NU7 was officially live and operating on the testnet environment.
The NU7 upgrade represents one of the most substantial structural adjustments to the Zcash network in recent years. Among its most prominent features is a massive reduction in the network’s target block spacing, which will drop from the historical 75 seconds down to just 25 seconds. By accelerating block production by a factor of three, the protocol aims to drastically improve transaction finality and overall user experience across the network.
In addition to faster blocks, the NU7 upgrade introduces several other critical protocol adjustments designed to modernize the blockchain’s architecture and improve its long-term economic model. The upgrade permanently disables version 4 transactions, removing legacy transaction formats that are no longer aligned with the network’s security and scalability standards. Furthermore, NU7 integrates a new Network Sustainability Mechanism, a feature engineered to automatically redirect a portion of network transaction fees back into future block rewards, thereby supporting the network’s ongoing security incentives.
However, the deprecation of version 4 transactions carries significant implications for holders of legacy assets. Specifically, disabling version 4 transactions means that any ZEC still held within Zcash’s legacy Sprout shielded pool will become entirely unspendable unless users actively migrate their funds to more modern shielded pools ahead of the full mainnet activation of NU7. This technical shift places an immediate responsibility on long-term holders and wallet providers to ensure that legacy funds are safely transitioned before the upgrade takes effect on the mainnet.
Following the successful testnet deployment, the Zcash Foundation issued a technical advisory on Friday encouraging all testnet operators, developers, and ecosystem participants to utilize the newly released code candidate to test NU7 under real-world conditions. This experimental phase is designed to surface any unforeseen bugs, consensus issues, or performance bottlenecks, allowing the engineering teams to verify network stability before making a final commitment to mainnet deployment.
The ongoing testnet evaluation period is brief but intensive. According to the current project roadmap, Zcash developers are scheduled to convene on Oct. 20 to review the performance of NU7 on the testnet. During this meeting, the core development group will make the final decision regarding mainnet activation and formally lock in the exact activation block height. If the testnet phase proceeds without major complications, the mainnet activation of the NU7 upgrade is tentatively slated for Nov. 5.
