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Zcash NU7 goes live at block 3,543,405 with 25-second target blocks

The NU7 network upgrade activated at 02:34 UTC on Nov 6. Target block time drops from 75 to 25 seconds; the Sprout pool is frozen; ZIP 218 caps per-block shielded activity.

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Zcash activated its NU7 network upgrade at block 3,543,405, mined at 02:34 UTC on Nov 6. The upgrade cuts the target block interval from 75 seconds to 25, caps per-block shielded transaction work via ZIP 218, redirects 60% of transaction fees to a future block-reward reserve, and permanently disables the legacy Sprout privacy pool under ZIP 2003. Reporting from CoinDesk ties the activation block to ZecStats data; the pre-activation slot and ZIP references were tracked in zcash/zips and our previous coverage (zcash-nu7-sprout-pool-freeze-zip-2003-block-3543405).

What happened

NU7 was the first mainnet upgrade since NU6.3 (the Ironwood activation at block 3,428,143, covered previously). The Zcash node team targeted a late Nov 5 ET window; activation landed at block 3,543,405 shortly after Thursday night ET (02:34 UTC Nov 6). By 04:59 UTC, the chain had produced 225 further blocks — an average inter-block interval near 39 seconds, with difficulty still adjusting toward the new 25-second target, per CoinDesk's reading of ZecStats.

No activation delay or reorg incident was reported in the first two hours. Payment finality on individual services still depends on each exchange's or wallet's own confirmation count.

What the upgrade changes

  • Block time. Target drops from 75 → 25 seconds. Capacity for simple shielded payments rises from roughly 3 to more than 6 per second (CoinDesk cites the upstream ZIP 218 analysis).
  • Shielded scanning cost. ZIP 218 caps the per-block shielded-transaction footprint so wallets can rule out blocks faster when looking for incoming notes. Estimated worst-case daily download drops from 271 MB to 169 MB.
  • Fees. Miners receive 40% of transaction fees; the remaining 60% flows into a reserve that begins feeding block rewards around February 2031. The 21-million-ZEC cap is preserved.
  • Sprout pool. The 2016-era Sprout privacy pool is retired: v4 transactions — the only format that can spend from Sprout — are rejected at the consensus layer. About 12,224 ZEC sitting in Sprout at activation becomes unspendable (co-founder Sean Bowe has sketched a possible future recovery ZIP; none is approved).

Early-run numbers

  • Activation block: 3,543,405
  • Activation UTC: 02:34, Nov 6, 2026
  • Blocks produced by 04:59 UTC: 225
  • Average inter-block interval in that window: ~39s (still converging)
  • Discarded-block rate in Zakura testing: 3.43% at 25s vs 1.57% at 75s
  • Sprout ZEC frozen at activation: ~12,224 ZEC
  • Governing ZIPs shipped: 2003 (Sprout freeze), 218 (shielded-scan caps)
  • Node software: Zakura-derived builds (Valar Group / Project Tachyon stress-tested 25s blocks on 80 nodes across 11 regions)

What to watch

  1. Difficulty retargeting pace: inter-block interval should converge toward 25s as the next adjustment windows land.
  2. Discarded-block rate on mainnet versus the 3.43% figure measured on the Zakura testbed.
  3. Whether any wallet or exchange posts a confirmation-policy update to reflect the faster blocks (wallets that assumed 75s cadence will finalize faster in wall-clock time).
  4. Any post-activation ZIP proposal restoring a one-way migration path for stranded Sprout balances.
  5. Fee-reserve accounting: the first on-chain accounting artifact is a reserve that holds the 60% miner-fee share until the 2031 feed-in; consistency between node builds matters.

Context

NU7 is the sixth consensus upgrade in Zcash's history after Overwinter (2018), Sapling (2018), Blossom (2019), Heartwood/Canopy (2020), NU5 (2022) and NU6/NU6.2/NU6.3 (2024–2026). The pattern is unchanged: deprecated transaction formats and old cryptographic constructions are cut out rather than carried indefinitely — the verifier is where soundness bugs live, and NU6.2 (zcash-orchard-nu6-2-emergency-hardfork) was itself the response to one. NU7 also lines up with the broader privacy-chain push on confirmation speed, which Aztec's testnet move to 12-second bridge-level finality tracked earlier this year (aztec-tierra-alpha-v6-upgrade-privacy-l2-proofs-12s-bridge).

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