Harmony Shuts Down Its Mainnet: What ONE Holders Must Check Before September 10

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.

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