Crypto · updated 2h ago · 2 min read
Zcash Activates NU7 on Public Testnet, Targeting 25-Second Blocks Ahead of Mainnet
NU7 activated on Zcash public testnet at block 4,465,026 on Oct 4. Block interval reduced from 75 seconds to 25 seconds under NU7.
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NU7 Testnet Goes Live
Zcash activated its NU7 network upgrade on the public testnet on October 4 at 18:21:45 UTC, when block 4,465,026 was mined on the Zcash testnet, according to data from the ZecBlock block explorer. Zcash’s NU7 consensus change targets a reduction in block spacing from 75 seconds to 25 seconds, and the upgrade is intended to improve transfer times for payment, deposit, and cross-chain transactions. Zcash’s Network Sustainability Mechanism redirects part of transaction fees into future block rewards, with NU7 taking 60% of transaction fees out of the system and allocating them to an account to pay for future emission costs.
Zcash also disabled version 4 transactions as part of NU7, a change that affects ZEC held in the legacy Sprout shielded pool because Sprout withdrawals require version 4 transactions. Zcash developers scheduled a final decision on mainnet activation for October 20, with the target date for NU7 going live on mainnet set for November 5.
Fees, Blocks, and Sprout
Zcash’s NU7 design keeps issuance from tripling even as blocks arrive more frequently, because the protocol adjusts block rewards to maintain a similar overall issuance rate despite the increased number of blocks. CoinDesk described the fee split under NU7 as miners receiving 40%, while the remaining 60% is removed from circulation and recorded in a reserve intended to fund future mining rewards. Zcash’s NU7 also adds restrictions on shielded transactions in each block, and the Zcash Foundation said the restrictions aim to improve shielded transaction capacity and reduce the maximum verification load that spam transactions could place on lightweight wallets.
Zcash’s NU7 disables transactions used by Sprout, Zcash’s oldest private-payment system, and holders with funds there would need to move them before mainnet activation to retain the ability to spend them through the existing system. Zcash Foundation urged testnet operators to deploy the release candidate under real network conditions, and Zcash testnet operators were told they did not need to make changes yet because no activation height had been established.
October 20 Decision Ahead
Zcash’s testnet phase places NU7 into live testing about a month before the planned November mainnet rollout, and the upgrade is active only on the public testnet for testing by network participants and other infrastructure providers.
Zcash developers planned to review test results on Oct. 20 and decide whether to proceed with mainnet activation, including choosing the block height at which the mainnet will activate.
Zcash’s NU7 test began at block 4,465,026 and was described as a public trial before a planned November rollout, with the earlier separate testing network shut down.
Zcash’s NU7 rollout also came with a stated warning that disabling version 4 transactions would leave ZEC held in the legacy Sprout shielded pool unspendable unless users move the funds before NU7 fully activates.
Zcash’s NU7 activation on testnet was confirmed in a post on X, and Zcash said NU7 was live on testnet as it moved the protocol changes into live testing ahead of the November target.