What is a network upgrade?
A network upgrade (sometimes called a "hard fork") is a coordinated change to the Zcash protocol rules. All nodes must update their software before the activation block height, at which point the new rules take effect. Unlike contentious forks in other cryptocurrencies, Zcash upgrades are planned collaboratively by the community and development teams.
Each upgrade activates at a specific block height — visible on the Dashboard's emission curve chart as milestones. The upgrades below are listed in chronological order.
Three threads run through Zcash's upgrade history. First, the steady advancement of privacy technology — from Sprout's pioneering but slow proofs, through Sapling's mobile-friendly performance leap, to Orchard's trustless Halo 2 proofs. Second, the evolution of network performance — Blossom's halved block time and NU5's more efficient transaction format. Third, the ongoing refinement of the funding model — from the original Founders' Reward, through the community-voted Dev Fund, to NU6's Lockbox approach that defers spending decisions to future governance.
Upgrade history
Genesis
Zcash launches with the Sprout shielded pool, bringing zero-knowledge proofs to a production blockchain for the first time.
- First cryptocurrency to implement zk-SNARKs in production
- Sprout shielded pool enabled private transactions (zc addresses)
- Equihash proof-of-work algorithm
- 12.5 ZEC block reward with 150-second block time
- Slow start: reward ramped from 0 to 12.5 ZEC over first 20,000 blocks
- Founders' Reward: 20% of block rewards to founders, investors, and developers
Overwinter
The first planned network upgrade, establishing the framework for future upgrades.
- Introduced versioned transactions (v3 format)
- Added transaction expiry to prevent stuck transactions
- Established the upgrade mechanism used by all future network upgrades
- Replay protection between upgrade branches
Sapling
A major leap in shielded transaction performance, making private transactions practical for everyday use.
- New Sapling shielded pool (zs addresses) with dramatically improved performance
- Shielded proof generation reduced from over a minute to just a few seconds
- Memory requirements dropped from gigabytes to ~40 MB
- Enabled shielded transactions on mobile devices and lightweight hardware
- Introduced viewing keys for selective disclosure
- Decoupled spend and output proofs for better efficiency
Blossom
Doubled network throughput by halving the block time.
- Target block time reduced from 150 seconds to 75 seconds
- Block reward halved from 12.5 ZEC to 6.25 ZEC to maintain same daily emission
- Halving interval adjusted from 840,000 to 1,680,000 blocks
- Effectively doubled transaction throughput capacity
- Reduced confirmation latency for all transactions
Heartwood
Enabled miners to shield coinbase rewards directly and added Flyclient support.
- Miners could now shield coinbase (mining rewards) directly to shielded addresses
- Previously, mining rewards had to go to transparent addresses first
- Added Flyclient protocol support for lightweight verification
- Improved privacy for miners and mining pools
Canopy
Coincided with the first halving. Ended the Founders' Reward and established the new development fund.
- Activated at the first halving — block reward dropped to 3.125 ZEC
- Founders' Reward ended permanently after 4 years
- New development fund: 20% of block reward split among ECC, Zcash Foundation, and community grants
- Block reward: 80% to miners, 7% to ECC, 5% to ZF, 8% to community grants
- Fund set to expire at the second halving (block 2,726,400)
NU5 (Orchard)
Introduced the Orchard shielded pool with Halo 2 — eliminating the need for a trusted setup ceremony.
- New Orchard shielded pool using the Halo 2 proving system
- No trusted setup required — a major security improvement
- Unified addresses (u1) bundle transparent, Sapling, and Orchard receivers
- Transaction v5 format with improved efficiency
- Orchard uses the Pallas/Vesta elliptic curve pair
- Backward compatible — Sapling and transparent transactions continue to work
NU6
Activated at the second halving. Introduced the Lockbox fund and restructured development funding.
- Activated at the second halving — block reward dropped to 1.5625 ZEC
- Introduced the Coinholder-Controlled Fund (Lockbox)
- Lockbox funds are locked on-chain and cannot be spent until future governance is established
- Block reward: 80% to miners, 8% to ZCG, 12% to Lockbox
- Zcash Community Grants (ZCG) became the sole active development fund recipient
- Lockbox accumulates ZEC for future community-directed allocation
Looking ahead
Zcash's upgrade history shows a community that consistently ships meaningful improvements while maintaining backward compatibility. Each upgrade has built on its predecessors — Sapling made Sprout's vision practical, Orchard eliminated Sapling's trusted setup requirement, and NU6 gave ZEC holders a direct stake in future governance through the Lockbox.
As the protocol continues to evolve, the patterns are clear: stronger privacy, better performance, and increasing decentralization of decision-making. You can explore the effects of these upgrades throughout this site — value pool trends on the Dashboard, block reward breakdowns on block detail pages, and transaction type distributions in the mining and block views.