How often do you sign a DeFi transaction and realize afterward that the numbers don’t match what you expected? Transaction simulation — the practice of running a dry‑run of a transaction before signing — is one of the clearest, under‑appreciated defensive moves an experienced DeFi user can take. It converts a black‑box interaction with a smart contract into an inspected, quantitative preview: estimated token balances, possible slippage, and visible side‑effects. For users who treat security as the primary product requirement of a wallet, simulation is not a nice‑to‑have; it’s a mechanism that transforms decision quality.
This article walks through how transaction simulation works, why it matters in practice (especially in the US regulatory and threat environment), how Rabby Wallet implements simulation and related defenses, and where simulations stop short. I compare transaction simulation to two alternative defenses — hardware wallets and approval management — to cla…