Zcash starts public test of 25-second blocks ahead of schedule

Zcash activated its NU7 upgrade on the public testnet on Oct. 4, moving the target block spacing from 75 seconds to 25 about two days before the scheduled date. The change went live at block 4,465,026, according to CoinDesk’s report. It gives node operators and other infrastructure providers a live test before developers decide whether to proceed with a planned November mainnet activation.

The timing is early against the published calendar, but the change remains confined to a test network whose coins have no monetary value. Zcash’s community timeline had set testnet activation for Oct. 6 and mainnet activation for Nov. 5. It also scheduled an Oct. 20 decision on whether to proceed and on the mainnet activation height. Those dates and upgrade features appear in the Zcash community’s NU7 timeline.

How much faster could confirmations become?

The target interval falls by two-thirds, from 75 seconds to 25. A service that continues to wait for three confirmations would have a target wait of about 75 seconds, down from 225, if block production follows the target and the service keeps the same confirmation rule. CoinDesk notes that actual block times vary, so the shorter target does not guarantee that every payment or exchange deposit will clear on that schedule.

The change also affects issuance mechanics. More frequent blocks would otherwise mean more rewards issued per unit of time. NU7 reduces the scheduled reward per block to one-third, according to CoinDesk, preserving Zcash’s issuance schedule as measured over time. That keeps the faster cadence from automatically tripling the creation of new ZEC.

What else changes with NU7?

NU7 allocates transaction fees between current and future mining rewards. Miners receive 40% of fees; the remaining 60% goes to a reserve intended to support future rewards as newly issued ZEC declines. The mechanism trades some current fee income for a pool that could help fund miners later. Its longer-term effect depends on future fees and the reserve’s operation; the testnet activation alone does not establish how much it will contribute.

The upgrade also disables transactions using Sprout, Zcash’s oldest private-payment system. Holders with funds in Sprout would need to move them before mainnet activation to retain the ability to spend them through the existing system, CoinDesk reports. The May NU7 testnet announcement described an earlier, temporary trial with a different feature set; this October activation is the public testnet phase tied to the planned mainnet schedule.

What will determine whether NU7 reaches mainnet?

The Oct. 20 review is the next scheduled decision point. Developers will weigh test results before setting an activation height or deciding whether to proceed, with Nov. 5 still the target rather than a confirmed mainnet activation. The test will also show whether the node software and related infrastructure can follow the new rules. CoinDesk reported that both major node programs, Zakura and Zebra, had released test versions ahead of activation, while the community timeline flags full nodes, indexers and block explorers as infrastructure that may be affected.

For users and exchanges, the relevant comparison is not just 25 seconds against 75. The test needs to show how block timing behaves in practice, whether services can support the upgrade, and whether the Sprout transition is handled before mainnet. Those results, alongside the Oct. 20 decision, will determine whether an early testnet start becomes a mainnet change on schedule.

Source material

• CoinDesk’s report — coindesk.com
• Zcash community’s NU7 timeline — forum.zcashcommunity.com