Duplicate Code Checker
Find copy-pasted blocks of code and see how much of a file is duplicated. Free and private: runs in your browser.
Paste one or more files. Repeated blocks of five or more lines are found even when indentation, comments or string contents differ.
Runs entirely in your browser. Nothing you paste is uploaded or stored.
Use cases
- Check a function before opening a pull request.
- Explain a review comment with numbers instead of opinions.
- Find the riskiest code to refactor first.
Frequently asked questions
How much duplication is acceptable?
Many teams aim for under 3–5% duplicated lines. Repeated logic should usually move into a shared function so a fix only has to be made once.
Is the Duplicate Code Checker free?
Yes. It is free with no sign-up, and it runs entirely in your browser, so your input is never uploaded or stored.
How accurate is a browser-based code check?
It uses fast heuristics on the snippet you paste, so it is great for quick feedback. For whole repositories, cross-file analysis and history, run a full CodeInspector scan.
Related tools
Track complexity, duplication and code smells across your whole codebase with CodeInspector.