Zcash NU7 Upgrade Puts $16 Million in Old Privacy Pool at Risk of Being Frozen
Zcash users are facing a final deadline to move funds out of the network’s oldest privacy pool, with approximately $16 million worth of ZEC at risk of becoming permanently inaccessible following an upcoming protocol upgrade.
Around 12,226 ZEC remained in the Sprout shielded pool as of Thursday morning, down from approximately 22,263 ZEC a week earlier, according to historical network data. The largest withdrawal activity took place on Sunday, when users moved roughly 9,094 ZEC out of the pool. Another 40 ZEC was withdrawn on Wednesday.
The deadline is linked to Zcash’s NU7 network upgrade, which will remove support for the older transaction format required to spend funds held in Sprout. Once the upgrade activates, users will no longer be able to move their remaining ZEC, even if they still control the private keys associated with their wallets.
Sprout was introduced when Zcash launched in October 2016. The privacy-focused network allows users to shield transaction details, including wallet addresses and transferred amounts. Over time, Sprout has been replaced by newer shielded pools that use more advanced privacy technology.
The Zcash blockchain had reached block 3,542,391 at 05:24 UTC on Thursday. With the current target block interval set at 75 seconds, the NU7 activation was expected in approximately 21 hours, potentially around 9:30 p.m. ET. However, differences in block production could push the upgrade into the early hours of Friday in Asia.
According to ZIP 2003, the technical proposal behind the change, NU7 will reject version-4 transactions. This is the only transaction format that supports spending funds from the Sprout pool, meaning any ZEC left behind will become inaccessible under the new network rules.
At a market price of approximately $1,300 per ZEC, the remaining 12,226 coins represent around $16 million. The final amount affected will depend on how much users withdraw before the upgrade takes effect.
The public balance does not reveal who owns the remaining funds or how many coins are held in wallets with lost private keys. However, users reviewing older wallet records can look for addresses beginning with the prefix "zc," which identifies Sprout addresses.
The upgrade will not remove the remaining coins from Zcash's total issued supply. ZIP 2003 leaves the door open for a future network change that could potentially restore access, although it does not guarantee that spending these funds will ever become possible again.
Removing Sprout support is also intended to reduce technical complexity and potential security risks. Maintaining outdated transaction systems creates additional work for developers and the network's validation software, particularly when the older pool sees relatively little activity.
Beyond the privacy pool changes, NU7 will introduce a major adjustment to Zcash's block production schedule. The target time between blocks will fall from 75 seconds to 25 seconds, allowing transactions to receive confirmations more frequently.
The upgrade therefore marks both the end of an older generation of Zcash privacy technology and a step toward faster block production.