cpd

jscpd

Copy/paste detector for source code — a fast Rust CLI that finds duplicated blocks across 223 languages, writes reports in 15 formats and can fail CI when duplication grows.

This crate is the Rust engine behind jscpd (v5+). Full documentation lives at jscpd.dev.

Install

cargo install jscpd
# or, without compiling (prebuilt release binaries via cargo-binstall):
cargo binstall jscpd

cargo install jscpd installs two binaries with identical behaviour: jscpd and cpd. The unrelated cpd crate on crates.io is not this project; the crate name is jscpd.

Also available on npm (npm install -g jscpd), Homebrew (brew install jscpd) and as prebuilt archives on the GitHub releases page.

Usage

jscpd .                                   # scan the current directory
jscpd src/ lib/                           # scan specific paths
jscpd --min-tokens 50 --min-lines 5 .     # tune sensitivity
jscpd --reporters json,html --output report .
jscpd --threshold 5 .                     # exit 1 above 5% duplicated lines
jscpd --blame .                           # annotate clones with git blame
jscpd --list                              # list supported formats
jscpd --help                              # every option

Config file

Options can also come from .jscpd.json in the scanned directory (or the jscpd key of package.json, or --config <path>):

{
  "minTokens": 50,
  "minLines": 5,
  "mode": "mild",
  "format": ["typescript", "javascript", "rust"],
  "ignore": ["**/node_modules/**", "**/dist/**"],
  "reporters": ["console", "json"],
  "output": "report",
  "threshold": 5
}

Reporters

Select one or more with --reporters (-r):

console, console-full, json, xml, csv, html, markdown, badge, sarif, ai, xcode, threshold, silent, openmetrics, codeclimate

Baselines and CI gating

# Record the current state, then fail only on clones that were not in it.
jscpd --update-baseline --baseline .jscpd-baseline.json .
jscpd --baseline .jscpd-baseline.json --fail-on-new-clones .

# Or compare against a git ref without a stored baseline file
# (the ref's tree is scanned with the same options).
jscpd --baseline-from-ref origin/main --fail-on-new-clones .

# Only the clones of the files git lists as changed; the first run saves
# the clones of HEAD as the baseline.
jscpd --changed .

MCP server

jscpd --mcp . scans the given paths, then serves the Model Context Protocol over stdio to MCP clients (Claude Code, Cursor, ...). Its tools (check_duplication, get_file_clones, get_statistics, check_current_directory, compare_folders) find exact, renamed, near-miss and semantic clones and compare two folders function by function.

Language server

jscpd --lsp serves the Language Server Protocol over stdio, so an editor shows clones, similar functions, semantic clones, dead code and complexity as diagnostics in the files you edit, updated as you type. See Editors for the setup in Neovim, Helix, Sublime Text, Emacs and JetBrains IDEs.

GitHub Action

- uses: kucherenko/jscpd@v5
  with:
    path: .
    threshold: 5
    reporters: console,sarif

Library use

The jscpd crate's library target is not a public API — it only exists to share helpers with the crate's tests and may change in any release. For programmatic use depend on the engine crates instead:

Crate	Purpose
cpd-finder	File walking, orchestration, git blame — the entry point
cpd-core	Detection algorithm (Rabin–Karp rolling hash), data models
cpd-tokenizer	Language tokenization (223 formats)
cpd-reporter	Output formatting (15 reporters)

use cpd_finder::orchestrate::{RunConfig, run};

let config = RunConfig {
    paths: vec!["./src".into()],
    min_tokens: 50,
    ..Default::default()
};

let result = run(&config).unwrap();
println!("Found {} clones", result.clones.len());
println!("Analyzed {} files", result.statistics.total.sources);

Links

• Repository: https://github.com/kucherenko/jscpd
• Documentation: https://jscpd.dev
• Changelog: https://github.com/kucherenko/jscpd/blob/master/rust/CHANGELOG.md

License

MIT