Mainnet

Mainnet is the main network of a blockchain, the one where coins have real market value and transactions are permanent. When people say a project has launched on mainnet, they mean its code is now running in production rather than in a test environment. Bitcoin's mainnet went live in January 2009; Ethereum's launched in July 2015.

Projects usually run on a testnet for months before a mainnet launch, and the phrase mainnet launch is often a major milestone that affects a token's price. Some projects launch a token before their mainnet exists, in which case the token trades on another chain and is migrated later.

Developers and users need to be sure which network a wallet is connected to. Sending mainnet funds to an address on the wrong network, or interacting with a test contract while believing it is live, can cause losses. Wallets typically display the active network name prominently for this reason.