Zcash’s Ironwood network upgrade, also known as NU6.3, is scheduled to activate on July 28, bringing changes to how shielded ZEC is moved and accounted for across the network.

The upgrade introduces a new shielded pool and a controlled migration mechanism known as a turnstile. After activation, the existing Orchard shielded pool will no longer accept new outputs, while new shielded activity will move to the Ironwood pool. The legacy zcashd client has also reached end of support, making Zebra the supported full-node path for operators.

According to the Zcash Foundation Zebra 6.0.0 release, Ironwood is set to activate on mainnet at block 3,428,143, expected around 13:00 UTC on July 28. The zcashd Book states that zcashd reached end of support on July 18 at block 3,417,100 and refuses to restart ahead of NU6.3. Operators are directed to run Zebra 6.0.0 or newer.

The main technical change concerns shielded pools. Orchard, which has carried private ZEC transactions for years, is being retired for new deposits and outputs after activation. A new Ironwood shielded pool will take over for new shielded activity, according to coverage of the NU6.3 rollout by crypto.news.

The turnstile is designed to control value leaving Orchard and entering the new pool. Rather than allowing funds to move unchecked between pools, the mechanism constrains and tracks migration so that third parties can independently compare totals and identify anomalies. The design was introduced after the Orchard vulnerability and is intended to support independent supply verification, according to the same crypto.news coverage.

That accounting boundary is especially relevant for a privacy-focused network because shielded transactions are designed to hide transaction details from public view while still requiring consensus rules that let the network maintain a verifiable supply. Ironwood’s migration path is therefore aimed at separating the privacy function of shielded transfers from the supply-accounting checks needed during a pool transition.

NU6.3 was already activated on testnet on July 4 at block 4,134,000, giving clients, wallet providers and services an opportunity to test tooling before mainnet activation, according to the zcashd documentation.

What changes at activation

Zcash upgrades activate at specific block heights, meaning new consensus rules take effect across the network at the designated block. For Ironwood, that height is 3,428,143 on mainnet, as configured in Zebra 6.0.0.

After that point, new shielded transactions are expected to use the Ironwood pool. Orchard will be retired for new outputs, although existing Orchard notes can still be migrated through the turnstile path. Transparent addresses are not changed by the upgrade; the major changes apply to shielded pools.

For users, the practical effect depends on the wallet or service they use. Updated wallets are expected either to handle migration automatically or provide a user flow for moving remaining Orchard notes through the turnstile. Wallets that have not shipped Ironwood support may mis-handle balances or require resyncing.

Users are advised in the source material to stop using Orchard addresses for new receipts after Ironwood is live, update wallets that add Ironwood support, and plan migrations if they still hold Orchard notes.

Key terms

Ironwood: The codename for Zcash’s NU6.3 network upgrade, which introduces a new shielded pool and turnstile rules.

Activation height: The exact block at which new consensus rules take effect. For Ironwood, Zebra 6.0.0 sets mainnet activation at block 3,428,143.

Orchard: The existing shielded pool that will be retired for new outputs once Ironwood activates. Existing Orchard notes can still be migrated through the turnstile.

Shielded pool: The cryptographic accounting environment where private ZEC transactions are recorded.

Turnstile: A controlled migration mechanism that constrains and tracks value leaving Orchard and entering the new Ironwood pool for supply verification.

Zebra: The Zcash Foundation’s full-node client. Version 6.0.0 configures Ironwood activation and is the supported path for mainnet after zcashd reached end of support.

Node and wallet operator checklist

Node operators and wallet backends should confirm their software versions before activation. zcashd 6.20.0 has reached end of support and will not carry nodes through NU6.3, according to the zcashd Book.

Operators are directed to install and sync Zebra 6.0.0 or newer. Zebra 6.0.0 sets the Ironwood activation height at 3,428,143 and was released on July 10, giving operators several weeks to deploy and observe a full sync before the July 28 activation.

Because Ironwood changes consensus rules at a fixed block height, infrastructure that has not upgraded may stop following the valid post-activation chain or fail to process the new shielded pool correctly. That makes coordination among nodes, wallet backends, exchanges and custodians part of the operational risk around the cutover.

Wallet and service operators should stop issuing Orchard addresses for incoming funds once the upgrade is live. After activation, new outputs to Orchard are retired by consensus and may not behave as users expect.

The source also recommends backing up wallet data, including seeds and relevant wallet metadata, before beginning any migration involving Orchard notes. If a wallet tracks Orchard notes, operators should ensure they have a reliable snapshot before migration.

After the new rules are live, operators are encouraged to test a small transaction in the new shielded pool to confirm their infrastructure is working correctly. Those holding Orchard notes should schedule migrations through the turnstile after activation and follow wallet-specific guidance, as implementations may stage migrations in batches.

Early after activation, services may monitor mempool activity and confirmations for unusual backlogs. Exchanges and custodians are also advised to update user-facing status pages so customers know which address types are accepted and whether maintenance windows apply.

Effect on everyday users

For users who mainly send and receive ZEC through a consumer wallet, the most visible change will be the location of private funds within Zcash’s shielded system. New shielded transactions will be created in the Ironwood pool rather than as new Orchard outputs.

Wallets that remain current may provide automatic migration or a one-click process for moving remaining Orchard notes through the turnstile. Users may see interface changes as developers add new address types, warnings and migration flows.

Transparent addresses remain unchanged. The upgrade is focused on shielded activity and the accounting relationship between the Orchard and Ironwood pools.

The network has tested NU6.3 on testnet since July 4, when the upgrade activated at height 4,134,000. That testnet activation gave clients and services a live rehearsal under the new rules, according to the zcashd Book.

The source states that the turnstile is intended for supply verifiability rather than reducing privacy. It constrains the accounting boundaries between pools so totals can be reconciled after the Orchard vulnerability discussed in July rollout coverage by crypto.news.

Zebra replaces the old zcashd stack

For infrastructure operators, the transition away from zcashd is central to the Ironwood upgrade. zcashd has halted after reaching end of support, while Zebra is maintained and configured for Ironwood.

Zebra 6.0.0 is actively maintained for NU6.3 and later network activity, with the activation height of 3,428,143 included in the release. zcashd, by contrast, reached end of support on July 18 at block 3,417,100 and includes auto-shutdown behavior before Ironwood, according to the zcashd Book.

The source describes Zebra as the recommended target for exchanges and custodians that need to maintain service after zcashd end of life. zcashd is described as the historical client, now frozen and no longer receiving future updates.

Operators that still have legacy infrastructure are advised to deploy Zebra alongside existing systems, fully sync it, and point a single wallet instance to it for a dry run before treating activation day as a maintenance window.

Migration scenarios and edge cases

Cold wallets that have not synced for months should be synced before activation so they can learn the final Orchard state under the old rules. That can make post-activation reconciliation smoother.

Exchanges should clearly communicate supported address types during the cutover. The source notes that temporarily disabling shielded deposits for a few hours around activation may reduce support issues, after which services can re-enable deposits using the new address format once backends confirm they are processing blocks after height 3,428,143.

Users with many Orchard notes are advised not to rush all migrations at once. Because the turnstile is designed for controlled flow, migrations may be batched in wallet-defined sizes. The source recommends logging transaction IDs and verifying balances after confirmations. If a wallet supports labels, users can tag each movement for later auditing.

Risks highlighted around activation

The main hazards identified in the source are outdated software, deposits sent to Orchard after activation, and mismatched wallet versions.

Running zcashd past July 18 is a risk because the client auto-halts and will not continue through activation. Sending to Orchard after activation may lead to failed deposits or funds not appearing where users expect, because new Orchard outputs are retired.

Unpatched wallets may mis-handle balances or become stuck resyncing if they have not shipped Ironwood support. The source recommends waiting for a wallet version that explicitly mentions NU6.3 readiness.

The source also warns against migrating shielded funds without a fresh seed and metadata backup, assuming instant finality immediately after activation, or failing to maintain an audit trail when moving many notes.

Frequently asked questions

When does Ironwood activate on mainnet?

Ironwood activates at block 3,428,143. Based on current block times cited in the source, that corresponds to around 13:00 UTC on July 28, according to the Zebra 6.0.0 release notes. The actual chain height, rather than a wall-clock estimate, determines activation.

Do users need to move funds out of Orchard immediately?

The source says no instant migration is forced, but users should stop using Orchard addresses for new receipts once Ironwood is live. Remaining Orchard notes can be moved through the turnstile path using an updated wallet.

What happens if zcashd is still running?

zcashd 6.20.0 reached its end-of-support halt on July 18 at block 3,417,100 and refuses to restart ahead of NU6.3. Operators need Zebra 6.0.0 or later to observe or validate post-activation blocks.

Are transparent addresses affected?

Transparent addresses are not changed by Ironwood. The main changes apply to shielded pools, including the retirement of new Orchard outputs and the introduction of the Ironwood pool.

Why is the turnstile needed?

The turnstile constrains and accounts for value moving from Orchard into the new pool, enabling independent verification of total ZEC supply after the Orchard vulnerability discussed in rollout coverage.

Was Ironwood tested before mainnet?

Yes. NU6.3 activated on testnet on July 4 at height 4,134,000, providing clients and services a live rehearsal under the new rules.

Will fees or confirmation times change?

The source states that no specific fee change is tied to activation. As with major upgrades, early hours after activation may see uneven mempool conditions while services adjust, so additional confirmations may be used for sensitive transfers.

Editor’s note in the source: In Q2 2026, Elliot Veynor wrote that he observed custody desks quietly spin up parallel Zebra nodes weeks before Ironwood and run dark traffic through them. He said the dry-run approach helped during testnet activation on July 4, when one vendor discovered a wallet indexing issue. He also wrote that smaller OTC desks were caught unprepared by the zcashd shutdown at block 3,417,100 and had to seek Zebra support by mid-July.

Disclaimer: This article is provided for informational purposes only. It is not offered or intended to be used as legal, tax, investment, financial, or other advice.