Zcash Sprout Pool Freeze Leaves About $16 Million in ZEC Stuck

Roughly 12,226 ZEC, worth about $16 million at recent prices, was still sitting in the Zcash Sprout pool on Thursday morning, according to CoinDesk, which cited ZecStats and Blockchair data. Once the NU7 network upgrade activates, those coins can no longer be spent with any supported software. The upgrade is set for block 3,543,405, which CoinDesk estimated would arrive around 9:30 p.m. ET on Thursday, Nov. 5.

Sprout is the original shielded pool that launched with Zcash in 2016. Newer pools called Sapling and Orchard replaced it years ago, and almost nobody uses it now. The upgrade does not burn the coins. It removes the only transaction format that can move them.

The Sprout freeze in eight numbers

• 12,226 ZEC: the balance left in Sprout early Thursday, per CoinDesk.
• 22,263 ZEC: the balance about a week earlier, before a late rush to exit.
• 9,094 ZEC: the amount that left the pool on Sunday alone.
• 40 ZEC: what moved out on Wednesday, a sign the exits had nearly dried up.
• About $16 million: the value of the remaining coins at roughly $1,300 per ZEC.
• 3,543,405: the mainnet block height where NU7 activates, as set in ZIP 259.
• 75 to 25 seconds: the cut in target block time that NU7 also brings.
• 60%: the share of transaction fees NU7 removes from circulation, one of the other changes listed in ZIP 259.

Why version 4 transactions are the whole story

The freeze comes from a rule change, not a decision aimed at Sprout holders. ZIP 2003 disallows all version 4 transactions from NU7 onward. Sprout transfers can only be written as version 4 transactions, so banning that format also disables Sprout spending.

The proposal is blunt about the reasoning. It calls Sprout "essentially unused," says the old code still adds a heavy load to the paths that accept new transactions, and points to denial of service risk in mempool and block processing. It also notes that zcashd, the only maintained software that still offered a Sprout wallet, was retired before the earlier NU6.3 upgrade.

One line is worth reading twice. ZIP 2003 says it does not propose to unissue or burn Sprout funds, but adds that the ability to spend them "may never be re-enabled." The coins stay counted in supply. They just cannot move.

What the falling balance says about who is left

The drop from about 22,000 ZEC to about 12,000 ZEC in a week shows some large holders were paying attention. The single 9,094 ZEC exit on Sunday accounts for most of that change. After that, flows slowed to a trickle.

What remains is likely a mix of lost keys, forgotten wallets from Zcash's early days and holders who never heard about the change. Without a maintained Sprout wallet, even people who know about the deadline face a technical hurdle. If you are new to how keys and addresses fit together, our guide on how crypto wallets work covers the basics.

ZIP 2003 also flags a privacy cost. It warns that a short or poorly coordinated exit period could make transaction timing and distinctive amounts easier to tie to particular holders, which cuts against the reason people used a shielded pool in the first place.

Wallets, exchanges and saved transactions

The rule reaches beyond Sprout. Every version 4 transaction becomes invalid after activation, including older Sapling and transparent ones, so services still building them need to switch. ZIP 259 tells wallets and transaction services to stop constructing version 4 transactions and to clearly report pending ones that become invalid. It adds that signing such a transaction again cannot make it valid, and that transactions saved or signed offline need the same checks.

Node operators who skip the upgrade may stay online but follow the old chain, which is why the ZIP asks for clear warnings to upgrade before activation.

If you hold ZEC on an exchange, the exchange handles this for you. If you keep coins in an old desktop wallet from Zcash's first years, check which pool they sit in before doing anything else, and be wary of anyone offering to "rescue" frozen funds for a fee. Our list of common crypto scam warning signs applies here. For background on how a network upgrade changes the rules every node follows, read what a blockchain is, and find more coverage on our crypto page.