What is mainnet?

The live network where transactions move real assets, as opposed to any test network running the same software.

Reaching mainnet is the milestone a project's roadmap points at, and it changes what a bug costs from an inconvenience to a loss. The word matters most at deposit time: an exchange address is valid on one specific network, and sending an asset over the wrong one is among the most common ways funds are lost.

Some projects launch a mainnet for a token that until then lived on another chain, and the swap is when exchanges pause deposits and convert balances for holders. Read that migration notice rather than assuming an ordinary transfer will be credited.

How it works

A blockchain's software can run several networks at once. They share the code and differ in the chain identifier they use, the genesis state they started from, and whether their coins have value. A test network issues its coins free from a faucet so developers can deploy and break things without cost. The mainnet is the one everyone else uses.

The separation is enforced by the chain identifier, which is included in what a transaction signs. That prevents a transaction created for one network being replayed on another, and it is why wallets ask you to switch networks rather than simply pointing at a different server.

Two practical situations follow.

1. Network selection on deposits and withdrawals. Exchanges list the asset and the network separately, because the same token exists on several chains and the same address format is used by many of them. Choosing wrongly sends real value to a network the recipient may not control, and support recovery is discretionary at best.
2. Mainnet migration. A project that launched its token on an existing chain and later ships its own network runs a swap. Exchanges pause deposits and withdrawals, convert held balances to the new asset, and resume. Holders in self-custody follow the project's own instructions, and the deadline is usually finite.

Running a testnet version of an application is normal practice up to launch. The distinction is worth keeping in mind when a project publishes usage figures, since testnet activity costs nothing and means nothing about demand.

Example

Illustrative walkthrough. You withdraw USDC from an exchange to a wallet. The withdrawal screen offers Ethereum, Arbitrum, Base, and several others. Your receiving wallet supports all of them, so any choice reaches you, and the cost differs by an order of magnitude. Now suppose the destination is another exchange's deposit address instead. That address is valid on one network only. Sending Base USDC to an address the venue monitors on Ethereum puts real funds at an address nobody is watching, and recovery depends on whether the venue controls that address on the other network and chooses to help.

Why it matters when you buy

Network selection is a real cost and a real risk on every transfer you make. Check what each venue supports on the exchange pages, compare withdrawal costs across networks on the fee comparison, and see sending crypto across chains for the procedure. The chain pages show measured throughput and fees per network.

Related terms

• testnet: the practice network running the same software
• chain id: what keeps networks from being confused
• deposit address: the network-specific destination
• genesis block: where a network's history starts
• layer 2: separate networks with the same address format
• token generation event: often the moment a mainnet asset appears

Questions

What happens if I send on the wrong network?

The funds arrive at that address on that network. Whether you can recover them depends on whether you or the recipient controls the address there, and on an exchange that is a discretionary support process.

Does a mainnet launch mean a project is finished?

It means the software is running with real value at stake. Most networks continue to ship substantial changes afterwards, and a launch is a starting point rather than a completion.

What is a mainnet swap?

A migration from a token on one chain to a native asset on the project's own network. Exchanges pause transfers and convert balances, and self-custody holders follow the project's instructions before a deadline.