Zcash's major network upgrade NU7 goes live on mainnet, cutting block time by threefold

Zcash Zcash (ZEC) announced that its major network upgrade, NU7, activated on the mainnet at block height 3,543,405 on Nov. 5.

The upgrade reduces the target block interval from 75 seconds to 25 seconds. Block subsidies are scaled down by the same factor so that the rate of new ZEC issuance remains essentially unchanged. The number of blocks between halvings is tripled, which preserves the existing halving schedule and the 21 million ZEC supply cap.

NU7 also activates the Network Sustainability Mechanism. The mechanism removes 60% of each block's transaction fees from circulation and stores it in a public reserve, with miners receiving the remaining 40%. The reserved fees are scheduled for gradual reissuance through block rewards beginning at block 8,939,664, expected to start in 2031.

"Like Bitcoin, Zcash faces a long-term challenge: how to sustain network security as block rewards decline. The NSM helps address that while preserving the 21 million coin cap," said Shielded Labs, an independent organization supporting the development of Zcash. The organization said NSM is its first major mainnet deployment on Zcash.

The upgrade also disallows version 4 transactions. As the original Sprout shielded pool relies exclusively on that format, any ZEC remaining in Sprout becomes unspendable. Approximately 12,224 ZEC sat in the pool at the activation height. 

Node operators were required to upgrade software before the activation height to remain on the consensus chain. The changes do not require significant updates for most wallets.

ZEC dropped 5.17% in the past 24 hours to trade at $1,254.7 as of 2:05 a.m. on Friday, amid a broader downturn in the crypto market. The GMCI 30 index, measuring the performance of the top 30 cryptocurrencies, is down 6.9%.