Zcash Developers Propose 20-Second Blocks in Draft NU7.1

Zcash's development team has proposed cutting block times to 20 seconds, a 20% reduction from the current 25 seconds, according to a draft Network Upgrade 7.1, or NU7.1, proposal published on the project's community forum.

The draft would increase block-production speed by 25%, the team said. Bitcoin.com reported on November 10 that the proposal was soliciting feedback, placing it just days after the activation of Network Upgrade 7, or NU7.

NU7 had already shortened Zcash's block time to 25 seconds from 75 seconds. NU7.1 now seeks another five-second reduction for services that need rapid transaction confirmation, including point-of-sale payments, exchange deposits and cross-chain swaps.

The draft's principal figures are:

• Block interval: 25 seconds to 20 seconds, a 20% reduction.
• Block-production speed: a 25% increase.
• Shielded actions per block: 330 to 264.
• Maximum block size: unchanged at 2 MB.
• Daily issuance and total supply: unchanged, including the 21 million ZEC cap.

What would NU7.1 change?

The proposal would move Zcash's block interval from 25 seconds to 20 seconds. The team described the faster cadence as a user-experience improvement for services dependent on quick transaction confirmation, rather than a revision to the chain's monetary framework.

NU7.1 would not change Zcash's daily issuance schedule or its 21 million ZEC supply cap. To account for the faster pace, the team proposed proportional changes to time-dependent parameters, specifically block subsidies and difficulty-adjustment windows.

The proportional adjustment would preserve the relationship between those time-based rules and the block cycle while leaving monetary policy unchanged. In operational terms, the network would produce blocks more frequently without changing how many ZEC enter circulation each day or the hard ceiling on total issuance.

Why would shielded-action limits fall?

NU7.1 would lower the maximum number of shielded actions allowed in each block from 330 to 264. The team said the reduction would avoid increasing the synchronization burden on light wallets and nodes as block times fall.

The 2 MB block-size cap would remain unchanged. The proposal would therefore tighten the limit on shielded operations per block without reducing the maximum size of a block, a distinction the team built into the draft.

What network risks remain?

Shorter block times could raise the orphan-block rate because network participants would have less time to propagate new blocks across Zcash before the next block arrives. The risk comes from propagation timing, even though the draft leaves monetary policy unchanged.

The team said data collected after NU7 and stress-test results showed that the orphan-block rate had instead declined. It still acknowledged that the risk could remain or increase if mainnet traffic surged, an operational condition the proposal does not eliminate.

Because NU7.1 leaves monetary policy untouched, the team said it “would represent a more limited change than NU7,” which had delivered the earlier cut from 75 seconds to 25 seconds. The contrast places NU7.1's 20% interval reduction and 25% production-speed increase within a smaller monetary-policy scope.

The proposal remains a draft. Its next formal steps are community review and a governance vote; without approval, Zcash's current 25-second block interval would remain in place, while approval would make 20 seconds the target interval.