Zcash Testnet Activates NU7 Upgrade with 25-Second Blocks and New Features

Zcash has implemented a network hard fork called NU7 on its testnet, bringing faster block times and new features to the protocol. The NU7 upgrade, which became active on the testnet in block 4,465,026 on October 4, introduces 25-second block times, improved shielded transaction features, and a Network Sustainability Mechanism (NSM).

The key change in NU7 is the reduction of block target spacing from 75 seconds to 25 seconds, which is expected to reduce the number of blocks during the current block target spacing interval to three. This will lower average first-block confirmation times from 75 seconds to 25 seconds, improving transfer times for payments, deposits, and cross-chain transactions.

The protocol adjusts block rewards to maintain a similar overall issuance rate despite the increased number of blocks. NU7 also adds restrictions on shielded transactions in each block, aiming to improve shielded transaction capacity and reduce the maximum verification load that spam transactions could place on lightweight wallets.

The Network Sustainability Mechanism, or NSM, redirects 60% of transaction fees to an account to pay for future emission costs, while the remaining 40% goes to miners. The upgrade will also block version 4 transactions on the live network, which could affect users with ZEC in Sprout shielded addresses.

NU7 is currently active only on the public testnet for testing by network participants and other infrastructure providers before mainnet activation. A Nov. 5 mainnet rollout is planned, but not confirmed, and developers will evaluate testnet results on Oct. 20 to decide whether to move forward with the mainnet rollout.