Payable Function Value Flow Tracer

WHAT IT DOES

Payable Function Value Flow Tracer helps developers and auditors understand how ETH moves through a contract when a payable function is called. You provide a contract address, a function signature, and an ETH value; the tool simulates the call and analyzes the bytecode to trace how the value flows — from the caller into the contract, and potentially onward to other addresses via transfers, calls, or selfdestruct. The output is a visual flow trace showing each step of the value's journey, helping you identify where ETH goes, whether it is forwarded, and if any unexpected transfers occur.

HOW TO USE

Enter the contract address and the function signature you want to trace (e.g., deposit(uint256 amount)). Optionally provide an ETH value in wei to simulate, and any arguments required by the function. You can also provide a custom RPC URL if you are not connected via wallet. Click "trace value flow". The tool encodes the function call, simulates it, and analyzes the bytecode for value‑moving patterns. Results show whether the function is payable, any gas estimate, and a step‑by‑step flow trace of where the ETH goes — including internal transfers, external calls, and selfdestruct destinations.

THE REAL MECHANISM

The tool uses ethers.js v5 to fetch contract bytecode and encode function calls using the contract interface. It simulates the transaction via eth_estimateGas to detect if the call would succeed or revert. The bytecode is then analyzed for known value‑moving patterns: transfer(), send(), call.value(), delegatecall, and selfdestruct. Each detected pattern is presented as a flow step in the trace. The tool also checks the EIP‑1967 implementation slot to detect proxies, which may delegate the value flow to an implementation contract. While the tool cannot fully execute the contract's logic without a full EVM simulator, it provides a heuristic view of likely value flows based on the bytecode structure.

WHAT IT CANNOT SEE

The tool cannot determine if value flows are secure, detect if value is lost or misappropriated without full execution, handle complex cross‑contract value flows, predict value flow through delegatecall (which may change the execution context), verify that value flows match business logic, or detect payable functions that rely on block context or state‑dependent conditions. The flow trace is a heuristic analysis based on bytecode patterns — it does not guarantee that the identified flows actually occur during execution. Always verify value flows through thorough testing and code review.

PLEASE NOTE — EVM CHAINS ONLY

This tool is designed for Ethereum Virtual Machine (EVM) compatible chains. It relies on EVM bytecode patterns and standard RPC methods. All processing occurs in your browser; no contract data is stored or transmitted.