Monero FCMP++: a new test network launches October 5 — what the major privacy upgrade changes for XMR holders
Right now, every Monero transaction hides the real sender among 16 candidates. After the FCMP++ upgrade there will be more than 150 million of them — the network's entire history. On September 25, developers released the third beta of the upgrade's test network, and it goes live on October 5. We look at what FCMP++ and Carrot change, when to expect them on mainnet, and whether you need to do anything with your XMR today.
How Monero hides the sender today
Monero hides three things in every transaction. Stealth addresses (one-time addresses) take care of the receiver: the wallet generates a new address for each payment, and an outsider can't link it to your public address. RingCT conceals the amount. The sender is covered by a ring signature: the wallet takes the real output being spent and adds 15 decoys pulled from the blockchain. From the outside you see 16 candidates, with no way to tell which one is real.
The ring size of 16 has been in place since the August 2022 hard fork. The problem with rings is that 16 is a small crowd. For years, researchers have been showing how decoy selection statistics, repeated use of the same outputs and exchange data can help narrow down the possibilities. None of this lets anyone trace Monero end to end, yet every bit of narrowing is a risk for users who count on privacy. The easiest way to narrow it down is data from exchanges that verify identity: the exchange knows who bought XMR and which address it went to. That's why it's more convenient to get your coins from a crypto exchange that needs no account and sends XMR straight to your wallet.
What FCMP++ changes
FCMP++ (Full-Chain Membership Proofs) replaces ring signatures with a zero-knowledge proof. The wallet proves that it is spending one of the outputs from Monero's entire history, more than 150 million so far, without revealing which one. Guessing the sender from decoys stops working once the candidate set is the whole network.
| Today | After FCMP++ | |
|---|---|---|
| Outputs the sender hides among | 16 | more than 150 million, every output on the network |
| How it is proven | ring signature with 15 decoys | full-chain membership proof |
| Addresses | standard | existing addresses keep working, Carrot is compatible with them |
| Custom unlock time for a transfer | can be set | feature is being removed |
About that last row: the option to lock a transfer until a certain block or date (unlock time) goes away when FCMP++ arrives. Developers explained that dropping it makes the upgrade easier to build into wallets. Transactions that have already been created are not affected.
What is Carrot
Carrot is Monero's new addressing protocol, launching alongside FCMP++. As the developers describe it, Carrot adds security, privacy and convenience features while staying compatible with existing addresses. In practice, you won't have to change your address or hand a new one out to everyone. You can keep using the same address when you swap Bitcoin for Monero or receive XMR from other people.
The latest beta already supports hot and cold wallets: a transaction can be built on an internet-connected device and signed on an offline one.
Where the upgrade stands
- More than two years of development. That's how long developers have already been working on FCMP++ and Carrot.
- Audit. From May 11 to 22, 2026, Trail of Bits reviewed the FCMP++ cryptography and its integration into Monero's code. The auditors reported six informational findings and no high-, medium- or low-severity issues; five have been fixed and one partially. The review covered the testnet code.
- September 25: stressnet beta v3.0. A stressnet is a test network for load testing. The new version brings hot and cold wallets, improved transaction relay between nodes, RandomX v2 (a new version of the mining algorithm) and bug fixes.
- October 5, block 3,102,800. The stressnet will split off from the Monero testnet. It is incompatible with previous versions, so participants will have to sync again from scratch.
- Mainnet: no date yet. In May, the official Monero blog wrote that no date had been set for the FCMP++ hard fork, and none has been announced since.
Anyone can watch the upgrade in action, since the stressnet is open to all. There's no real XMR on it, and anonymity is close to zero: it has dozens of participants, against thousands on mainnet. On top of that, a stressnet node reveals your IP address to other participants.
What XMR holders should do now
- Nothing urgent. Your coins and addresses remain yours; the upgrade changes the rules for new transactions.
- Update your wallet once the date is announced. You'll need a version that supports FCMP++: after the hard fork, older versions won't be able to send transactions.
- Be ready for exchange pauses. Around a hard fork, platforms usually halt XMR deposits and withdrawals for a while.
- Watch out for "migration" offers. You don't need to move your coins anywhere. Offers to "swap your XMR for new coins", "update your wallet via a link" or "enter your seed phrase to migrate" are scams.
Monero and Zcash: two approaches to privacy
In September, Zcash grabbed the market's attention, nearly doubling in 30 days. Privacy in Zcash is opt-in: coins are hidden only if their owner has moved them into the shielded pool. Monero hides everything for everyone by default, and FCMP++ expands that protection dramatically. A similar idea is being tried for Bitcoin too — we covered how Bitcoin could get Zcash-style private transactions.
ZEC holders who want privacy by default can swap Zcash for Monero without registration.
How to buy Monero
You won't find Monero on the biggest exchanges, so the easiest way to get it is through a swap. You can swap bitcoin for it or convert USDT TRC20 to XMR straight into your own wallet. All the options are collected in our guide on how to buy Monero when major exchanges don't list it.
Swapping on VertEXchange doesn't require an account: you enter your Monero wallet address, and the coins are sent straight to it.
Frequently asked questions
What is FCMP++ in Monero?
An upgrade that replaces 16-member ring signatures with a zero-knowledge proof: the sender hides among all outputs on the network, and there are more than 150 million of them.
When will FCMP++ launch?
No mainnet date has been set. On October 5, 2026, a new version of the test network (the stressnet) with FCMP++ and Carrot goes live.
Do I need to do anything with my XMR?
Not right now. When the hard fork date is announced, update your wallet. There's no need to move your coins, and anyone asking for your seed phrase "for the migration" is a scammer.
Will Monero addresses change?
No. Carrot, the new addressing protocol, is compatible with existing addresses.
Will Monero be traceable after FCMP++?
Analyzing ring decoys will become pointless, because every output on the network will be a candidate. Off-chain leaks remain: data held by exchanges that verify identity, your IP address and your own behavior. We looked at where they come from today in our article on whether Monero can be traced.
What is Carrot?
Monero's new addressing protocol, launching together with FCMP++. It adds security, privacy and convenience features and works with older addresses.
What is a stressnet?
A test network for load testing the upgrade. It has no real XMR, and privacy there is minimal because there are too few participants.
Swap bitcoin for Monero without registration: XMR goes straight to your address.
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