Harmony Mainnet Shutdown on September 10: What ONE Holders Should Know Now the Deadline Has Passed

Harmony is giving up its own blockchain. On September 6, 2026 the team behind the network announced that it will shut down the mainnet it launched in 2019 and reissue the ONE token as an ERC-20 token on Ethereum. For you as a holder, one point matters above all: if your ONE sit inside a smart contract, meaning a liquidity pool, a multisig wallet or a DeFi position, you have to pull them out beforehand. Those positions do not travel with the migration. Balances in an ordinary wallet and on an exchange, by contrast, are captured by a snapshot and credited again on Ethereum without you having to apply for anything.

The window is tight. Reports name both September 9 and September 10, 2026, and they do not name them consistently. Anyone affected should therefore not wait until the last day.

Harmony mainnet shutdown: what happens on September 9 and 10, 2026

A mainnet is the productive main network of a blockchain, where real balances and real transactions live, as opposed to a testnet. Harmony runs such a mainnet as an independent layer 1 chain. Layer 1 describes a blockchain that settles and secures its transactions itself instead of attaching itself to another chain.

That independence is now ending. According to the announcement, the final blocks are to be processed on September 9, 2026; validators may shut down their nodes afterwards. On the exact cut-off date the available reports diverge, and you should know that rather than have it smoothed over: The Block writes that users should exit all smart contracts before September 10, 2026, and names September 10 as the day validators are allowed to cease operations. ETHNews describes September 9 as the day of the final blocks and September 10 as a hard boundary after which funds in certain positions are lost. The Chinese-language industry outlet WuBlockchain names September 9 in its summary as the deadline for exiting smart contracts.

In practice the spread means this: anyone holding a position on Harmony has until September 8 to unwind it safely. After that it depends on whether the chain is still producing blocks, and that is not something to rely on when money is at stake.

Why Harmony is abandoning its own chain: the cross-shard exploit of August 12

The trigger lies four weeks back. On August 12, 2026 Harmony was attacked through a flaw in what is called cross-shard verification. Harmony splits its network into shards, several parallel sub-chains that settle transactions among themselves via receipts. The attacker was able to have valid receipts redeemed more than once. The result was new ONE with no offsetting entry: the attack touched not a single smart contract. It struck one level deeper, at the consensus layer, the place where the network's nodes agree on the valid state.

The scale is the reason an in-flight repair was ruled out. The first confirmed wave covered around 4 billion ONE, which against a total supply of roughly 15.01 billion works out at about 26 percent. Reconstructing the full attack, the security firm Verichains arrived at roughly 3.01 trillion forged ONE. The two figures do not contradict each other; they describe different stages of the post-mortem.

Harmony then opted for a rollback, winding the chain back to a state before the attack. Shard 0 was reset to block 92,730,034 and shard 1 to block 94,978,278; both checkpoints carry the same timestamp, 23:25:37 UTC on August 11, 2026, shortly before the first confirmed forgery. More than 141,000 consecutive blocks and over 109,000 regular transactions were discarded, 109,441 exactly according to ETHNews, along with several hundred staking operations. What such a reversal means for your own holdings and for your holding period is set out in our explainer on the blockchain rollback after an exploit.

The reasoning behind the current shutdown reaches beyond this single case. In the project's words: “The threats posed by state actors and AI agents are too great.” That is the team's assessment, not a verified fact, and it stands that way in the announcement.

Snapshot and airdrop: how ONE becomes an ERC-20 token on Ethereum

A snapshot is a point-in-time record of all balances at a defined block. Harmony intends to take that record at the chain's final block and then distribute new ONE as an ERC-20 token on Ethereum to the same addresses. ERC-20 is the standard on which the vast majority of tokens on Ethereum are built; it defines how a token is transferred and queried, so that wallets and exchanges can support it without special handling.

For the majority of holders that is the good news: there is no claim process, no form, no redemption deadline. Anyone holding ONE in a self-custodied wallet whose address also works on Ethereum will be credited the new tokens there automatically. Total supply and issuance rate are to remain unchanged. Newly issued tokens are to be allocated to Harmony's own new venture, an initiative around AI-assisted video production that the team describes as a “remix economy”. Whether that pivot carries is an open question, and not a decisive one for the deadline at issue here.

Not every address is alike: the difference between the ONE and Ethereum formats

Harmony uses two notations for addresses: the familiar Ethereum format beginning with 0x, and its own format with the prefix one1. Both denote the same key, merely encoded differently. If you hold your ONE in a wallet where you own the private key or the seed phrase yourself, that is uncritical for the migration, because the same key also controls the matching 0x address on Ethereum.

It becomes critical somewhere else: with addresses that belong to a program and not to a key. That is exactly what the next section is about.

Balances on an exchange: why you usually have nothing to do here

If your ONE sit on a centralised trading platform, the address belongs to the exchange, not to you. According to the announcement the snapshot also captures holdings on centralised exchanges, and Harmony intends to switch the listings over to the new token. In that case the exchange credits you the ERC-20 token once it has worked through the changeover.

Even so, you should not rely on that blindly. A chain shutdown is a separate operation for every platform: it has to halt deposits and withdrawals on the old network, add the new contract and trigger the credit. Experience shows that exchanges announce this in their announcements section, often only a few days in advance, and that the suspension of deposits usually comes first. So check your platform's notices, and move no ONE to or from it in the days around the cut-off. If in doing so you find that your exchange does not list the token at all, or that its communication stays thin, a sober look at the alternatives helps: our comparison of the best crypto exchanges shows which providers handle changes of this kind cleanly on a regular basis.

Liquidity pools, multisig and DeFi: what the migration leaves behind

This is where the actual work lies. According to the announcement, multisig safes, liquidity pools and on-chain applications cannot be migrated. Users are told to exit all smart contracts before the cut-off date.

A liquidity pool is a contract into which several users deposit two tokens so that others can swap between them for a fee; your share of it is represented by a dedicated pool token. A multisig safe is a wallet that requires several signatures for a payout, technically also a contract rather than an ordinary address. What both have in common is that program code sits behind the address instead of a private key. That is precisely why a snapshot can allocate nothing to you there: on Ethereum that contract does not exist, and no one can rebuild it for you.

The task is therefore clearly defined. Go through the applications in which you have ever deposited anything on Harmony, and pull the holdings back to an address whose key you hold yourself. That applies to pool shares as much as to collateral posted in lending contracts, to wrapped tokens and to anything you brought onto the chain via a bridge. If you no longer remember where everything sits, the chain's block explorer helps: it lists all token balances for your address and the contracts you have interacted with.

For the wallet you pull everything back into, one plain rule applies: it has to be an address whose seed phrase you own. An address inside an application that has never shown you the private key is not a safe choice for this purpose.

Staking delegations and validators: where the rewards end up

Anyone who has staked ONE has as a rule delegated them. Delegation means assigning your tokens to a validator who takes part in consensus on your behalf, without you giving up control over them. The validator in turn is the operator of a node that proposes and confirms blocks and is rewarded for doing so.

A special rule applies to these holdings, and it is the point at which many holders are likely to be unpleasantly surprised: delegated stakes and rewards not yet claimed are not to flow directly to wallets, but into governance treasuries, referred to in the announcement as governor vaults. A treasury in this context is a jointly managed pot whose use the community decides on. Your delegated ONE will therefore not land automatically in your wallet as a freely available ERC-20 token.

If you want to keep control, undelegate before the cut-off date and claim your outstanding rewards, so that both sit as ordinary balance on your own address. Bear in mind that unwinding a delegation carries a waiting period on many networks. Check in your wallet menu how long yours runs before you count on the final day. Harmony has pledged to support validators in moving into roles within the new venture; for you as a delegator that is no substitute for exiting yourself.

ONE in trading: what our count of trading venues on September 7 shows

This analysis was carried out by cryptoticker.io itself on September 7, 2026. It is based on CoinGecko's public dataset on Harmony: we counted every trading pair listed there, each with its trading venue, currency pair and reported daily volume.

The result is sobering, and directly relevant to the question of how you act now. Thirty trading pairs across 23 trading venues were recorded. The price stood at $0.00073244, or €0.0006309, the market capitalisation at around €9.38 million, rank 1168. For comparison: before the attack ONE was still traded as a project with a billion-dollar valuation. The dilution from the forged tokens and the rollback have all but wiped out the market value.

Two things stand out when you look at the venues. First, volume is heavily concentrated: Binance accounted for around $481,000 in daily volume with ONE/USDT and around $212,000 with ONE/TRY, followed by Pionex, OKX, Gate, KuCoin and MEXC in the mid five-figure to low six-figure range. Second, there is almost no euro access: among the 30 pairs we found exactly one euro pair, ONE/EUR on OKX, with a reported daily volume of around $533. Providers through which German investors usually trade did not appear in the list at all.

It remains open which exchange has already committed to the switch to the ERC-20 token. Three entries were flagged as anomalies in the dataset and one more as stale; we left them in the count but did not use them as a reliable volume figure. And the volume figures come from the trading venues themselves, they are not independently audited.

What follows for you is above all an expectation: selling larger holdings in euros will founder on these volumes. Anyone wanting to sell has to go via a stablecoin, and anyone unwilling to do that holds the position and waits for the migration.

Tax and holding period: what the swap can trigger for German investors

Caution is warranted here, and in both directions. The framework is settled: in Germany, gains from selling crypto assets held as private assets count as a private disposal transaction under section 23 of the Income Tax Act, with a holding period of one year, after which a disposal gain remains tax-free. The Federal Ministry of Finance last set out the cooperation and record-keeping obligations for crypto assets in more detail in its circular of March 6, 2025.

What is not settled is how this particular event is classified. Whether crediting a new ERC-20 token after the original chain is shut down is to be treated for tax purposes as a swap that starts a fresh holding period, or as a mere continuation of the same asset, has not been decided for this case. We are not asserting a legal position that does not exist in this form. What you can do in practice is document: record which holdings you had at which point in time on which address, when the credit occurred and at what price. Without those records, any later classification, whichever way it falls, is barely traceable. Only a tax adviser can give you binding advice on your own case.

Layer 1 shutdown as a risk: how to spot an endangered chain early

The Harmony case stands at the end of a development that is visible across several smaller chains. From the sequence of events you can derive markers that you can check on any chain where you hold meaningful balances.

How many validators actually carry the network?

A rollback across 141,000 blocks presupposes that a manageable number of operators can agree on a new version within days. That is practical when an attack has to be repelled, and at the same time it shows how narrow the circle is that decides on the valid state. Check how many independent validators there are and how much stake falls to the largest among them.

How much of your holdings sits in contracts rather than in a wallet?

The expensive part of this migration hits positions in smart contracts and nothing else. Anyone simply holding a balance in a self-custodied wallet gets through by doing nothing. This asymmetry applies to almost every chain wind-down. On a small chain the extra yield from a liquidity pool is rarely worth the risk of no longer being able to pull it out when it matters.

How quickly do the trading venues react?

For most holders the exchange is the real lifeline, because it goes through the snapshot and handles the changeover. The fewer venues list a token, the greater the chance that nobody takes on the work. Our count above shows how thin that cover has become for ONE.

Is there a bridge, and where does it end?

A bridge connects two blockchains and gives you on the destination chain a claim on a holding that is locked on the origin chain. If the origin chain is switched off, the value of that claim depends on whether anyone can still release the lock. Wrapped tokens are therefore among the positions you unwind first.

Checking the Harmony shutdown: what to take away

1. Open your wallet today and look for contract positions. Pool shares, collateral in lending contracts, wrapped tokens and multisig holdings all go back to an address whose seed phrase you hold yourself. If you notice in the process that your current wallet setup does not even show you what you have deposited where, that is the real finding: our software wallet comparison ranks the common applications by exactly that question.
2. Undelegate your staking positions and claim outstanding rewards. Delegated holdings and unclaimed rewards are to go into governance treasuries, not into your wallet. Factor in the waiting period when unwinding. For amounts you then want to hold longer term, separate custody is the soberer choice; which devices are suited to it is covered in the hardware wallet comparison.
3. Check your exchange's notices and move nothing in the days around the cut-off date. Deposits and withdrawals on the old network are, in experience, halted first, and a transfer that falls into that window is the most common way to lose holdings. If your platform is regularly late or silent on changes like this, the exchange comparison lists the providers that handle it more reliably.

You can read the announcement itself in the project's own channel: Harmony on X, September 6, 2026. A detailed write-up of the figures on the rollback and the compensation has been published by ETHNews; it also puts a number on the compensation of $1.372 million, which is to be paid out over four quarters.

(As of September 7, 2026. This article is not investment advice. Prices and fee structures change; check the terms with the provider before you buy.)