Essentially, a mainnet swap consists of switching from one blockchain network to another. In most cases, the swap takes place when a cryptocurrency project migrates from a third party platform (e.g., Ethereum) to their own native blockchain network. At this point, their cryptocurrency tokens are gradually replaced by newly issued coins and all blockchain activity is moved to the new chain.
Therefore, a mainnet swap takes place when a blockchain project replaces previously issued tokens with their new cryptocurrency, which is typically running on their own blockchain network. This process may also be referred to as “token migration”. Usually, the mainnet swap begins right after the mainnet launch.
It should be noted that the migration of tokens is not always associated exclusively with the launch of a new blockchain. It may also take place in situations where projects simply move from one protocol to another. For example, Storj performed a mainnet swap, migrating their tokens from a Bitcoin-based protocol to the Ethereum network as a way to avoid scalability problems.
Each mainnet swap has its own particularities in terms of execution. Some projects assign migration periods, with a predefined deadline for users to exchange their old tokens for the new ones. If they fail to do so, they may end up losing access to their funds because the old tokens are usually destroyed or frozen.
In contrast, the mainnet swap performed by Binance gave users the freedom to leave their BNB tokens on their Binance account, so the swap could be automatically done by Binance team. In fact, the swap was performed through withdrawal requests. In other words, by keeping their ERC-20 BNB on their Binance account, users could later withdraw the newly issued BEP2 BNB in equal amounts, without having to worry about manually swapping their tokens.