Code Duplication Detector Across Contracts

WHAT IT DOES

This tool detects code duplication across multiple smart contracts by comparing function bodies and identifying similar patterns. It analyzes verified source code from multiple contracts, comparing function implementations to find duplicated or nearly duplicated code segments. The tool calculates similarity scores between functions across contracts, identifying pairs with high duplication levels that may indicate copy-paste patterns or opportunities for code reuse. Results are presented as a detailed duplication report with similarity percentages, duplication severity levels (high/medium/low), function pair mappings, and actionable recommendations. This is essential for developers reducing code redundancy, auditors identifying maintenance risks, and teams improving code quality across contract ecosystems.

HOW TO USE

Connect your wallet (read-only, no transaction required) and select the target network. Enter contract names (optional) and addresses as a comma-separated list. Click "detect code duplication" and the tool will verify each contract, fetch its source code, and compare function bodies across all contracts. Results display a summary with duplication counts by severity level, detailed duplication cards showing each duplicate pair with similarity percentage, function names, and level-specific recommendations, and a table of all detected duplicates with their similarity scores. Use the report to identify candidates for refactoring, reduce code redundancy, and improve maintainability.

TECHNICAL MECHANISM

The detector uses ethers.js v5.7.2 to perform a multi-stage duplication analysis. First, it calls eth_getCode to verify each contract is deployed and uses block explorer APIs (Etherscan, Sourcify) to fetch verified source code and ABI for each contract. The tool parses each contract's source code to extract function definitions and their bodies, using a combination of regex-based pattern matching and tokenization to normalize code for comparison. For each pair of functions across different contracts, it calculates a similarity score using a token-based comparison algorithm that accounts for structural patterns, variable names, and control flow. The similarity score ranges from 0% to 100%, with higher scores indicating greater duplication. Functions are classified into duplication levels: high (≥85%), medium (65-84%), and low (50-64%). Each duplicate pair receives a recommendation based on its severity level—high duplication should be extracted to a shared library, medium duplication should be evaluated for consolidation, and low duplication may be acceptable. Results are compiled into a structured report with detailed function pair information, similarity metrics, and actionable recommendations.

WHAT IT CANNOT SEE

This tool cannot detect duplication in contracts that are not verified or have opaque implementation details where source code is not available. It is limited by the availability and completeness of source code verification—if the source code is not fully verified or is obfuscated, the analysis may be incomplete. It cannot detect semantic duplication where code is functionally similar but syntactically different (e.g., different variable names or different ordering of operations that produce the same logic). The analysis relies on the accuracy and completeness of source code parsing and comparison algorithms; syntax errors or non-standard patterns may produce inaccurate results. It cannot analyze contracts that are not deployed or have been self-destructed. The tool is limited to the specific contract instances and source code versions that are accessible via RPC and block explorer APIs. It cannot guarantee that detected duplication reflects actual code reuse or copy-paste patterns without manual review—some similar code may be intentional and necessary for different use cases.

PLEASE NOTE

This is a read‑only analytics tool—it never submits transactions or modifies contract state. It is designed for EVM‑compatible chains and works best with verified contracts that have clean, parsable source code. The duplication report is for informational and code quality purposes only and should not be considered a comprehensive code review. Always manually review detected duplication to determine if refactoring is appropriate for your specific use case. The tool's similarity thresholds are heuristic—adjust them based on your project's code quality standards.