Zcash has activated its NU7 network upgrade on testnet, moving a planned set of protocol changes into live testing roughly one month before the upgrade's targeted mainnet rollout.

A testnet is a parallel network where upgrades run without value at stake, giving node operators a venue to exercise consensus changes before they reach mainnet. According to ZecBlock, a block explorer for the Zcash testnet, block 4,465,026 — NU7's scheduled activation point — was mined on Oct. 4 at 18:21:45 UTC. Zcash confirmed the activation in a post on X, saying NU7 was live on testnet.

What NU7 changes

NU7 is Zcash's next network upgrade. It seeks to reduce the network's target block spacing from 75 seconds to 25 seconds, and it also disables version 4 transactions. Target block spacing is the interval the protocol aims for between successive blocks, so a shorter target means new blocks are produced more often. In addition, the upgrade integrates a Network Sustainability Mechanism that redirects a portion of transaction fees into future block rewards.

The planned removal of version 4 transactions carries a direct consequence for holders: ZEC held in Zcash's legacy Sprout shielded pool would become unspendable unless users move their funds before NU7 fully activates. Sprout is the oldest shielded pool on the network, dating to Zcash's 2016 launch, and version 4 is an older transaction format that predates the version 5 format introduced with the NU5 upgrade.

Testing timeline and mainnet decision

The Zcash Foundation said on Friday that testnet operators should use the release candidate to test NU7 “under real conditions.” The testnet phase gives developers an opportunity to assess the upgrade before deciding whether to proceed with mainnet activation.

Zcash developers are scheduled to make a final decision on mainnet activation and set the upgrade's activation height on Oct. 20, based on their experience with NU7 on testnet. Mainnet activation is targeted for Nov. 5.

Zcash is a privacy-focused cryptocurrency whose shielded payments rely on zero-knowledge proofs, and protocol changes such as NU7 are introduced through its numbered network upgrade process. For Sprout holders, the Oct. 20 decision and the Nov. 5 target effectively frame the remaining window to move legacy funds while version 4 transactions are still supported.