Transaction Simulator

Preview Transaction Outcomes

Simulate transactions before executing them to preview exact outcomes, gas costs, and potential errors on a forked mainnet environment.

Transaction Preview & Simulation

This tool allows you to simulate transactions on a forked mainnet to see exact outcomes.

Transaction Simulation and Testing

Learn how transaction simulation helps you avoid costly mistakes and understand exactly what will happen before sending transactions on-chain.

Why Simulate Transactions?

Transaction simulation allows you to test complex DeFi interactions, preview state changes, and identify potential failures before spending gas. This is especially valuable for high-value transactions or complex smart contract interactions.

How Simulation Works

Simulators create a fork of the current blockchain state (usually closest to the latest block) and execute your transaction in this isolated "sandbox" environment. It runs the EVM exactly like a real node but discards the result instead of broadcasting it.

Common Revert Reasons

Execution Reverted: Generic error, often due to requirement checks (`require()`) failing in the smart contract (e.g., trying to transfer more than balance).
Out of Gas: Transaction limit lower than needed execution cost.
Slippage Limit Exceeded: Output amount detected is less than minimum spec.

Advanced Features: State Overrides

Advanced simulators allow "State Overrides". You can pretend an account has more ETH than it really does, or pretend a contract variable is different, allowing you to test "what-if" scenarios (e.g., "What if I was a whale?") without owning the funds.

Frequently Asked Questions

Yes, simulating transactions doesn't cost gas since nothing is actually executed on-chain. It's a risk-free way to test your transactions and debug failures.

Simulation catches most errors (logic bugs, reverted requirements), but blockchain state can change between simulation and execution (e.g., price moves, front-running). Always verify conditions.

Timing. The state of the blockchain (balances, prices, nonces) changed between the moment you simulated and the moment your transaction was mined. High volatility increases this risk.

Yes! This is a great use case. If the simulation of a 'sell' transaction reverts or shows 100% tax, you know it's a scam token without risking real gas fees.

A call trace shows the internal chain of smart contract calls made during the transaction. It helps developers debug exactly which line of code caused a revert.

Modern wallets like Rabby or Phantom perform auto-simulation to show you the expected balance change ('You will lose 1 ETH, You will receive 2000 USDC'). If this preview is missing or red, be careful.

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