kucherenko/jscpd

> Duplicate code detector for 220+ languages — plus dead code, complexity hotspots, duplication and health trends over git history, and one health score for the whole codebase. Rust engine, self-contained binary, AI-ready with an MCP server and a token-efficient reporter.
**Documentation:** https://jscpd.dev
jscpd tokenizes each of its 224 supported formats the way that language defines it — its own comment and string rules, not generic text — then finds duplicated token sequences across files with a rolling Rabin-Karp hash. Opt-in passes catch copies that differ only in names or values (Type-2) or that have a few edited lines (Type-3), and an experimental one uses a code embedding model for functions that do the same thing written differently (Type-4). See How detection works for the full mechanism, and Supported formats for the full list.
Beyond duplicates, jscpd also finds dead code (--dead-code), ranks files by complexity (--complexity), tracks duplication and health over git history (--history), and rolls it all into one health score (--health) — see Features below.
Quick Start
Then scan a project:
Other install methods
| Method | Command | Notes |
|--------|---------|-------|
| npm | npm install -g jscpd | Installs the jscpd command; prebuilt binary, no Node.js at runtime |
| npm (cpd command) | npm install -g cpd | Same binary, exposed as cpd |
| PyPI | pip install jscpd | Platform wheels with both commands; also pipx install jscpd, uv tool install jscpd, or uvx jscpd . to run without installing |
| Cargo | cargo install jscpd | Builds from crates.io; installs both jscpd and cpd |
| Homebrew | brew install jscpd | macOS / Linux |
| Nix | nix run github:kucherenko/jscpd -- /path/to/code | Or nix profile install github:kucherenko/jscpd |
| Docker | docker run --rm -v "$PWD:/src" ghcr.io/kucherenko/jscpd . | Multi-arch image built from the release binaries |
GitHub Action
Uploads SARIF results to GitHub Code Scanning by default. See CI & Pre-Commit Hooks for all inputs and outputs.
Documentation
| Document | Description |
|----------|-------------|
| Rust engine | Installation, CLI reference, reporters, baseline, summary, complexity, dashboard, blame, config file |
| AI-Ready | AI reporter, agent skills, MCP server |
| Editors | jscpd --lsp, the language server: setup for Neovim, Helix, Sublime Text, Emacs and JetBrains IDEs |
| Programming API | Rust API (cpd-finder crate) |
| CI & Pre-Commit Hooks | GitHub Action, Docker image, pre-commit hooks |
| Packages | npm packages and crates that make up a release |
| Supported formats | All 224 formats with their file extensions |
| Runnable demos | One fixtures/ -demo/ directory per feature, each README lists the commands with their expected output |
Features
jscpd v5 is a Rust engine that ships as a self-contained binary — no runtime required — under two npm names (jscpd installs the jscpd command, cpd installs cpd), on PyPI, crates.io, Homebrew, Nix, Docker, and as a GitHub Action.
Duplicate detection
- **Language-aware tokenization** — per-format comment and string syntax for all 224 formats, the oxc parser for JavaScript/TypeScript/JSX/TSX, embedded-language extraction for Vue, Svelte, Astro, Markdown and Razor, and keyword/identifier/literal classification, so a clone is a repeated sequence of *language tokens*, never a repeated run of text (see How detection works)
- **224 language formats**, with cross-format detection (Vue SFC, Svelte, Astro, Markdown) and --cross-formats groups to match clones across JavaScript and TypeScript
- **Type-2 clones** — --ignore-identifiers, --ignore-literals and --ignore-annotations find blocks that differ only in names, literal values or annotations, reported as renamed (see docs)
- **Type-3 near-miss clones** — --max-gap-lines N merges a copy with a few inserted or changed lines into one similar clone with a similarity score; --similarity compares whole functions of JavaScript, TypeScript, Python, Java, Kotlin, Scala, C#, Go, Rust, C, C++, PHP, Ruby, Swift and Clojure by the subtrees of their normalized syntax trees, in code blocks of Markdown and components as well: renamed locals and other literals match, other called functions or operators do not, and test files are left out; the edn reporter lists every pair with its score (see docs)
- **Type-4 semantic clones (experimental)** — --semantic embeds the functions of JavaScript, TypeScript, Vue, Svelte, Astro, Python, Rust, Go, Java, Kotlin, C#, C, C++, PHP, Ruby, Scala and Swift files with a code embedding model, either one jscpd runs itself (after jscpd --semantic-download once) or any OpenAI-compatible API, and reports functions that do the same thing written differently: the same feature implemented twice in one language, or a rule your Rust backend enforces and your Svelte frontend repeats (see Semantic clones below)