Web3 Onboard simulates transactions using our state-of-the-art mempool platform so that you can preview transactions to see net-balance changes and gas spent before committing them on-chain. This allows users to know exactly what their net balance changes will be and avoid scams. Developers can also use this to help with testing and debugging transactions committed on-chain. See more [here](https://onboard.blocknative.com/docs/modules/transaction-preview). 