Zcash NU7 Testnet Activation Speeds Up Block Time by Threefold

Zcash has taken a significant step towards faster transaction processing with the activation of its NU7 network upgrade on the public testnet. The upgrade, which was initially estimated to go live on October 6, was activated at block height 4,465,026 on October 4. This marks the first live run of 25-second blocks, a threefold speedup from the current 75-second target block spacing.

The NU7 upgrade is designed to improve the efficiency of point-of-sale payments, exchange deposits, and cross-chain bridges. The upgrade leaves the coin's 21 million supply cap and four-year halving schedule unchanged, but introduces a Network Sustainability Mechanism. This mechanism removes 60% of each block's transaction fees from circulation into a reserve, while miners keep the other 40%. The reserve is designed to provide a predictable source of funding for network security once block rewards shrink.

The testnet activation is the first time the changes run on a live network, and the Zcash Foundation is seeking feedback from operators before a mainnet decision on October 20. The Foundation has set a target of November 5 for the mainnet activation, following a coin-holder vote that backed the faster blocks while preserving halvings.

The NU7 upgrade also tightens shielded transaction limits, which is expected to more than double Orchard throughput while reducing the worst-case sync load a spammer can impose on light wallets by about 37%.