Zcash NU7 Upgrade Explained: Faster Blocks and the Frozen Sprout Funds

Zcash’s NU7 network upgrade activated at block 3,543,405 in the first days of November 2026, cutting the network’s target block time from 75 seconds down to 25 seconds — about three times faster — and shortening how long a typical payment takes to confirm. The upgrade also disabled an older transaction format, which had the side effect of permanently locking roughly 22,000 ZEC that was still sitting in Zcash’s original, long-unused shielded pool.

If you hold ZEC, use Zcash for payments, or just saw “NU7” trending and want the short version: block times got faster, confirmations got quicker, and a small, mostly-dormant pool of old coins is now stuck. Here’s the detail behind each piece.

What NU7 Actually Changed

NU7 — short for “Network Upgrade 7,” Zcash’s seventh major protocol-level upgrade — targets one core problem: Zcash’s blocks were slow. Under the previous rules, the network aimed for a new block roughly every 75 seconds. Under ZIP 218, the Zcash improvement proposal that defines the change, NU7 cuts that target to 25 seconds, a two-thirds reduction in block spacing.

The activation itself is tied to a specific block height rather than a calendar date — ZIP 259 set it at block 3,543,405 — which is why the “November 5” target that developers agreed on in late September ended up landing closer to November 6 once actual block production was accounted for; independent trackers like cryptoticker.io flagged that slippage days ahead of activation based on how fast blocks were actually arriving.

To avoid changing Zcash’s monetary policy, developers also reduced the per-block mining subsidy to about a third of its prior size — three times more blocks per hour, each paying roughly a third of the previous reward, so total ZEC issued per hour and the project’s 21 million coin supply cap are unaffected. NU7 changes the clock speed, not the money supply.

Why Faster Blocks Matter: Confirmation Times

The practical upside of a shorter block interval is faster payment confirmation — the thing that actually matters to someone sending or receiving ZEC.

	Before NU7 (75-second blocks)	After NU7 (25-second blocks)
Target block spacing	~75 seconds	~25 seconds
Typical first confirmation	~75 seconds	~25 seconds
Three-confirmation wait (common exchange requirement)	~4 minutes	~75 seconds
Per-block mining subsidy	Full amount	~1/3 of prior amount (offsetting faster blocks)

According to a KuCoin flash report published around activation, merchants and exchanges that require multiple confirmations before treating a Zcash deposit as final see that wait drop from around four minutes to roughly 75 seconds — a meaningful change for any business or exchange using ZEC for payments or withdrawals, where confirmation delay is a direct cost.

It’s worth noting that a brand-new target doesn’t mean the network hits it instantly. Right after an activation like this, actual block times can run slower than the new target while the network’s difficulty-adjustment algorithm catches up to the change — a normal, temporary phase for any blockchain that resets its block-time target, not a sign something is broken.

The Side Effect: Sprout Funds Are Now Frozen

The more disruptive part of NU7 has nothing to do with speed. As part of cleaning up older protocol code, NU7 disables “version 4” transactions across the entire network. That matters because version 4 is the only transaction format that can spend coins out of Sprout — Zcash’s very first shielded (private) transaction pool, active since the network’s 2016 launch and effectively superseded years ago by two newer, more efficient shielded pools called Sapling and Orchard.

Once version-4 transactions stopped working at activation, any ZEC still parked in Sprout became unspendable. Reporting from KuCoin and Cointelegraph in the weeks before activation put the amount at roughly 22,000 to 22,300 ZEC — an estimated $26 million based on mid-October 2026 pricing — a small slice of Zcash’s total circulating supply, but real money for whoever still holds those keys.

Developers gave the community an explicit heads-up before the cutoff, and coverage from Bankless described holders as having roughly two weeks’ warning to move any remaining Sprout balances into a newer pool before the deadline. What happens to the ZEC that didn’t move in time is still an open question in the Zcash community: a proposal on the project’s GitHub (zcash/zips issue #825) suggests eventually burning the stranded Sprout funds and redirecting their value to the Zcash Sustainability Fund, but as of the upgrade’s activation that’s a community proposal, not a decided outcome.

Two things are worth being clear about if you hold ZEC: this only affects the old Sprout pool specifically. Transparent (non-private) addresses, the newer Sapling and Orchard shielded pools, and ZEC held on exchanges are all unaffected by the version-4 change — you don’t need to move funds out of those to stay safe.

How NU7 Compares to Other Recent Protocol Upgrades

NU7 sits alongside a wave of 2026 blockchain upgrades aimed at squeezing more speed out of established networks rather than chasing entirely new designs — Ethereum’s Glamsterdam upgrade and Solana’s Alpenglow upgrade both targeted faster finality and confirmation times earlier this year, for comparison. Zcash’s version is narrower in scope: one targeted change to block cadence, paired with a cleanup of old transaction code, rather than a broad rework of the protocol’s execution layer.

The tradeoff NU7 makes — breaking compatibility with a legacy feature (old-format Sprout spends) in exchange for a simpler, faster network — is a familiar pattern in mature blockchains that have accumulated years of legacy code paths few users still rely on.

Price Reaction

ZEC’s price moved on the news well before activation itself. Cointelegraph reported the token rallying about 12% in late October 2026 — trading near $1,270 at the time, according to CoinGecko data cited in that report — right around when developers finalized the block-height target for activation, suggesting traders were pricing in the upgrade’s completion rather than waiting for the live event itself. That followed an already volatile few months for ZEC; for the fuller picture of Zcash’s 2026 price run — including the Grayscale ETF conversion and the broader privacy-coin rally that preceded this upgrade — see our earlier explainer on Zcash’s 2026 price rally.

As with any crypto asset, a protocol upgrade going smoothly is not a price prediction, and ZEC’s history this year shows it can give back a rapid run-up just as fast as it built one.

What to Watch Next

A few things are worth tracking in the days and weeks after activation, rather than assuming everything settled instantly:

• Whether block times stabilize near the new 25-second target. Expect a short adjustment period as mining difficulty retargets to the faster schedule.
• Node software compatibility. Zcash runs on two independent full-node implementations (zcashd and the Rust-based Zebra); both needed updated releases supporting the NU7 activation height, and any node still running outdated software will fall out of consensus with the upgraded network.
• Exchange and wallet support. Services that interact with Zcash — especially any that still reference Sprout addresses in old documentation or support flows — may need updates reflecting that pool’s new frozen status.
• Whatever happens to the stranded Sprout balance. The GitHub proposal to eventually burn and redirect those funds is unresolved; if the community acts on it, that’s a separate decision from NU7’s activation itself.

None of this is financial advice. Zcash remains a smaller, more volatile asset than Bitcoin or Ethereum, and protocol upgrades — even ones that go cleanly — don’t eliminate the regulatory and exchange-access risks that have followed privacy coins for years. Anyone holding or using ZEC should do their own research and double-check with their wallet or exchange provider if they’re unsure which shielded pool their funds are in.

Sources: KuCoin — Zcash’s NU7 Upgrade Activated, Private Payments Confirm 3x Faster, KuCoin — Zcash’s NU7 Upgrade to Freeze Sprout Pool, Rendering Funds Unspendable, KuCoin — Zcash NU7 Upgrade Imminent, 22,000 ZEC at Risk of Soft Freeze, KuCoin — Zcash Jumps 12% After NU7 Upgrade Activation Height Finalized, Cointelegraph — Zcash (ZEC) rallies 12% as NU7 mainnet upgrade nears, Coinpaprika — Zcash’s NU7 Upgrade Triples Payment Speed, Freezes Its Oldest Privacy Pool, Bankless — Zcash Sprout Holders Have Two Weeks to Move Their ZEC, CryptoTicker — Zcash falls ahead of block 3,543,405, the NU7 cut-off for old Sprout funds.