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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 .

MCP server

jscpd --mcp . scans the given paths once, then serves the Model Context Protocol over stdio, exposing check_duplication, get_statistics and check_current_directory tools to MCP clients (Claude Code, Cursor, ...).

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

License

MIT