If you hold any ZEC that has remained untouched in Sprout, the network’s original shielded pool, an upcoming upgrade may make those coins inaccessible even if you still control the keys.
ZecStats data updated on Thursday showed roughly 12,224 ZEC still sitting in Sprout. At recent prices that represented about $15–16 million that could become effectively frozen once the NU7 network upgrade activates.
“NU7 (block 3,543,405) makes v4 transactions invalid, so what remains in Sprout is unspendable: frozen, not burned,” ZecStats noted in its Sprout information card.
Sprout introduced zero-knowledge proofs when Zcash launched in 2016. Later privacy systems—Sapling, Orchard, and Ironwood—followed. The pool has been closed to new deposits for years, yet holders could previously move existing coins out. NU7 invalidates version-4 transactions, the only format that can spend from Sprout. According to the network specification, those transactions will become invalid after activation at block 3,543,405, which was expected Thursday evening in the United States.
The change addresses long-standing maintenance burdens: supporting the original privacy system demanded heavy computing resources and carried verification risks that developers want to remove.
The coins themselves are not destroyed. They will continue to count toward Zcash’s circulating supply. A future upgrade could theoretically restore spending capability, the specification notes, but “spending may never be re-enabled” and the team has not shown interest in doing so. ZecStats describes the funds as frozen, not burned.
Legacy holders face the greatest exposure. Anyone whose ZEC remains in Sprout must move it through a compatible withdrawal mechanism before the upgrade activates or risk indefinite inaccessibility. Sprout addresses begin with “zc,” a useful clue for spotting old wallet records. Users on modern wallets that never touched Sprout do not need to take action beyond keeping their software updated.
The blockchain cannot identify owners of the remaining balance, so it is impossible to know how much belongs to active users versus keys that have already been lost.
For everyone else, NU7 shortens Zcash’s target block interval from 75 seconds to 25 seconds according to the Zcash Foundation, allowing first confirmations roughly three times faster.
As of publication the chain stood at block 3,543,027; activation was expected later that Thursday at block 3,543,405.
