Zcash NU7 Enters Testnet With 25-Second Blocks

Zcash has activated its NU7 network upgrade on testnet, beginning a testing period for changes that would shorten block intervals and modify mining rewards. The planned November 5 mainnet rollout also carries a deadline for holders of legacy Sprout funds, which will become unspendable under the new rules unless users move them beforehand.

The activation occurred at testnet block 4,465,026, and developers will use testnet results to decide whether the upgrade is ready for the main network.

Zcash NU7 Mainnet Decision Scheduled for October 20

The development team plans to decide on October 20 whether to proceed with mainnet activation and select the corresponding block height. November 5 remains the target date, subject to that review.

Meanwhile, the Zcash Foundation has asked testnet operators to run the NU7 release candidate under real-world conditions. Testing will assess network behavior as the target block interval falls from 75 seconds to 25 seconds.

That change would produce blocks three times as frequently. However, the per-block reward will fall to one-third of its previous level, preserving the existing issuance schedule. The upgrade retains Zcash’s traditional halving structure and maximum supply of 21 million $ZEC.

Legacy Sprout Holders Face a Migration Deadline

Alongside faster blocks, NU7 will disable Version 4 transactions. That change will prevent users from spending funds remaining in Sprout, Zcash’s original shielded pool, after mainnet activation.

Affected holders must transfer their $ZEC to a supported address before the upgrade takes effect. Sprout shielded addresses begin with “zc,” distinguishing them from newer address formats.

The migration requirement concerns funds in that legacy pool. Moving those balances before activation will allow holders to retain access under the updated network rules.

Infrastructure operators also face requisite preparations. The legacy zcashd node software will not support NU7’s consensus changes, which will require operators to migrate to compatible implementations such as Zebra or Zakura.

Transaction Fees Will Support Future Mining Rewards

NU7 will also introduce a Network Sustainability Mechanism that changes how the network distributes transaction fees. Under the mechanism, miners will receive 40% of those fees, while the remaining 60% will be allocated to a reserve for future mining rewards.

Meanwhile, exchanges, explorers, and indexers must prepare their systems for the shorter block interval. Mining pools must also update their node software to follow the new consensus rules. Developers will review testnet performance before confirming the mainnet activation height at the October 20 decision.

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