Zcash Activates NU7 on Public Testnet, Opening a Trial Run for 25-Second Blocks

Zcash’s NU7 Upgrade Goes Live on Testnet – 25‑Second Blocks in Action

Zcash’s long‑awaited NU7 network upgrade has just activated on its public testnet, cutting the block interval from 75 seconds to a brisk 25 seconds. The change, which will be rolled out to mainnet in early November, is a key step toward faster payments and a more responsive network while keeping the daily supply of new ZEC unchanged.

What the Upgrade Means for Block Times

The testnet activation occurred at block 4,465,026 on October 4, two days ahead of the original schedule. A live dashboard shows a median block time of 19.5 seconds across the latest 300 blocks, with the target of 25 seconds still being fine‑tuned. By producing blocks three times as often, Zcash can deliver confirmations faster for point‑of‑sale transactions, exchange deposits, and cross‑chain bridges—areas where the previous 75‑second interval was a bottleneck.

Keeping the Supply Stable

Faster blocks might suggest a higher issuance rate, but NU7 keeps the daily supply of new ZEC constant. Each block’s reward is divided by three, and the halving schedule is stretched accordingly. In addition, 60 % of transaction fees are routed into a reserve for the Network Sustainability Mechanism, leaving miners with 40 % of fees. Coinholders voted in September to start paying back this reserve via block rewards in February 2031.

Shielded Pools and Spam Mitigation

NU7 introduces caps on shielded activity per block. Under the new limits, Orchard’s throughput can more than double, while the maximum slowdown a spammer can impose on light‑wallet syncing drops by roughly 37 %. The upgrade also disables v4 transactions, effectively suspending Sprout, Zcash’s original shielded pool. Funds left in Sprout after the upgrade will be inaccessible.

Next Steps: Mainnet Activation

The testnet activation height was set in version 1.6.0 of the Zakura node software (released October 1) and the Zebra candidate (released October 2). Developers will review testnet data and decide on the mainnet activation height on October 20. The planned mainnet launch is November 5. According to co‑founder Sean Bowe, the upgrade should not affect wallets, but full nodes, indexers, and block explorers may need adjustments.

Bottom Line

Zcash’s NU7 testnet run demonstrates that the network can handle 25‑second blocks without inflating the supply or compromising security. The upgrade paves the way for faster, more efficient transactions on mainnet while preserving the economic model that underpins ZEC.

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TL;DR: Zcash’s NU7 upgrade, now live on testnet, cuts block times to 25 seconds, keeps daily ZEC issuance stable, caps shielded activity, and sets the stage for a November mainnet launch.