Assembly-Level Instruction Tracer

WHAT IT DOES

Assembly-Level Instruction Tracer is a developer-focused tool that traces EVM assembly-level instructions from transaction hashes. It takes a transaction hash and optional contract bytecode and ABI from the user, then fetches the transaction and receipt via eth_getTransactionReceipt. The tool disassembles the contract bytecode into individual EVM opcodes, showing each instruction's program counter (PC), opcode name, gas cost, pushed values (for PUSH instructions), and a preview of the stack state. The trace categorizes instructions by type (default, revert, call, return) and color-codes them accordingly. Results are displayed with a summary showing the transaction details, bytecode size, total instructions, and a detailed instruction trace with gas costs. This enables developers to debug smart contract execution at the lowest level, identify gas-intensive operations, and understand the flow of instructions during transaction execution.

HOW TO USE

Connect your wallet to the target EVM chain. Enter a transaction hash into the input field. Optionally, paste the contract bytecode and contract ABI (JSON format) for additional context. Click "Trace instructions" to disassemble and trace the execution. The tool will display a summary including the transaction details, bytecode size, and total instructions traced. The instruction trace shows each opcode with its program counter, name, gas cost, and a stack preview. Instructions are color-coded: revert (red), call (purple), return (green), and default (teal). The trace can be copied or downloaded as JSON.

TECHNICAL NOTE: EVM OPCODE DISASSEMBLY AND SIMULATION

The tool disassembles the contract bytecode by parsing each byte and mapping it to its EVM opcode using a comprehensive opcode map. For PUSH instructions, the tool extracts the pushed value. The tool also simulates a basic execution context by tracking gas costs for each instruction using approximate gas costs from the EVM specification. When the transaction receipt is available, the tool displays the actual gas used. The tool supports optional ABI decoding for call data, though the primary focus is on the assembly-level instruction trace. The trace is limited to a maximum of 200 instructions for performance, but the full trace data is available in the JSON output.

WHAT IT CANNOT SEE

The tool cannot trace transactions without internal trace data; it relies on the transaction receipt and bytecode disassembly. It is limited to the accuracy of the provided trace data and the opcode map. It cannot decode custom opcodes without the EVM specification. The tool is limited by debug_traceTransaction availability on the RPC endpoint for advanced tracing. It cannot trace transactions on non-EVM chains. It cannot guarantee that the trace is complete or accurate, as the simulation is based on disassembly and may not perfectly reflect actual execution.

PLEASE NOTE

This tool is designed exclusively for EVM-compatible chains (Ethereum, Polygon, BNB Chain, Arbitrum, Optimism, Avalanche C-Chain, etc.). It does not support non-EVM blockchains. The instruction trace is based on bytecode disassembly and may not capture all execution paths or runtime behavior. For accurate execution traces, use an RPC endpoint that supports debug_traceTransaction. The tool is read-only and does not modify any state. The tool provides no warranty that the trace is complete or accurate; users should verify with additional debugging tools.