This describes the shift of a crypto project from one independent blockchain to another. Mainnet swap can be properly explained as the migration or movement of tokens from a third-party network to the token’s native blockchain.
This usually happens when a project uses another blockchain during its testing phase. For instance, before the launching og BNB, Binance used the Ethereum blockchain for testing. After completing the testing phase and launching of the mainnet, holders of thet ERC-20 BNB token were told to migrate to the BEP2 BNB coin.