Overview

Alchemy’s Transaction Simulation API lets developers and users preview on‑chain transactions before execution. By simulating single or bundled transactions, it provides clear insights into asset movements, ABI‑decoded execution traces, logs, and potential errors. This pre‑execution visibility empowers wallets, dapps, marketplaces, and security tools to enhance user safety, cut gas waste, and prevent fraud—all across Ethereum, Polygon, Arbitrum, Optimism (soon) and Base.

Features and Capabilities

• Asset Changes Simulation – Returns sanitized data detailing token and asset deltas (transfers, approvals) before execution.
• Execution Simulation – Enables full EVM simulation with ABI‑decoded execution, comprehensive logs, events, traces, and gas usage.
• Bundle Simulation – Simulates multiple sequential transactions, persisting state between each, ideal for multi-step interactions (e.g., approve → swap).
• Multi‑chain Support – Works across Ethereum Mainnet & Goerli, Polygon Mainnet & Mumbai, Arbitrum Mainnet & Goerli, with Optimism support launching soon.
• Enhanced Security – Helps catch scams and malicious contracts by exposing potentially harmful or erroneous transactions before signing. ~$5B in crypto scams in 2022 underline importance.
• Gas‑Efficient – Prevents the cost of reverted transactions by simulating them, saving unnecessary gas fees.
• Developer Ergonomics – Accessed via a single method in the Alchemy SDK with support for different simulation depth levels.
• Use‑Case Diversity – Fits wallets (balance previews), security tools, DEXs (slippage & approval insight), NFT marketplaces (safe listing/purchases), lending protocols, MEV/trader tooling, smart‑contract testing (even in production forks).
• ERC‑4337 UserOp Simulation – Supports smart account (User Operation) simulation to preview using ERC‑4337 flows via Alchemy Account Kit.