jscpd

jscpd is a duplicate code detector written in Rust and shipped as a self-contained binary. It tokenizes each of its 224 supported formats using that language's own comment and string rules, then finds repeated token sequences across files with a rolling Rabin-Karp hash. JavaScript, TypeScript, JSX and TSX are parsed with the oxc parser, and embedded languages are extracted from Vue, Svelte, Astro, Markdown and Razor files. Run it with jscpd /path/to/code.

By default it reports exact clones. Opt-in flags extend detection: --ignore-identifiers, --ignore-literals and --ignore-annotations find Type-2 clones that differ only in names or values. --max-gap-lines N and --similarity 0.85 find Type-3 near-miss clones. The experimental --semantic flag uses a code embedding model to find functions that do the same thing written differently (Type-4). --compare dirA/ dirB/ pairs functions across two codebases to show what has no counterpart in the other. Results can be filtered by kind with --kind, and --skip-local and --skip-isolated limit reports to cross-folder or cross-team duplication in monorepos.

Beyond duplication, it has --dead-code (unused files, exports, declarations and imports in JavaScript, TypeScript and Python), --complexity and --summary for ranking files and folders, --history for duplication trends across a git commit range, --blame for author comparison, --dashboard, and --health for a single 0-100 score. There are 15 reporters, including console, json, xml, csv, html, markdown, badge, sarif, codeclimate, openmetrics and an ai reporter. A baseline mode (--baseline, --fail-on-new-clones) fails CI only on newly introduced clones.

Integrations include a GitHub Action that uploads SARIF to Code Scanning, GitLab-compatible report artifacts, pre-commit hooks, an LSP server (jscpd --lsp) for Neovim, Helix, Sublime Text, Emacs and JetBrains IDEs, and an MCP server and agent skills for AI agents. It targets developers and teams who want to gate CI on duplication or track code quality over time. It installs through npm, PyPI, Cargo, Homebrew, Nix and Docker.

Installation

# via Homebrew
brew install jscpd

# via npm
npm install -g jscpd

# via Cargo
cargo install jscpd