jscpd — Copy/Paste Detector

jscpd v5.x is the Rust-based engine — 24-37x faster than v4. For the TypeScript/Node.js version (programmatic API, LevelDB/Redis stores), see jscpd v4.x.

Fast copy/paste detector for programming source code. Supports 223 language formats, 13 output reporters, and per-line author attribution via git blame. Prebuilt binaries for 6 platforms — no Node.js runtime required.

Packages

| Package | Installs | Use it when | |---------|----------|-------------| | jscpd@5 | jscpd | Same command name as v4; drop-in CLI replacement | | cpd | cpd | Shorter command name only | | jscpd (crates.io) | jscpd + cpd | Rust-native install; both binaries |

The npm jscpd@5 package installs a single jscpd command that runs the same Rust binary as cpd. For the shorter cpd alias on npm, install the separate cpd package.

Performance

| Codebase | Files | Size | jscpd v4 (Node.js) | jscpd v5 (Rust) | Speedup | |----------|-------|------|--------------------|-----------------|---------| | Multi-format fixtures | 548 | 1.5 MB | 1.03 s | 0.03 s | 34.3× | | Svelte source | 9K | 38 MB | 15.80 s | 0.43 s | 36.9× | | CopilotKit | 17K | 159 MB | 82.89 s | 3.44 s | 24.1× |

Methodology: docs/performance-comparison.md.

Install

# npm — installs the jscpd command
npm install -g jscpd

# crates.io — installs both jscpd and cpd binaries
cargo install jscpd

# Nix — run without installing
nix run github:kucherenko/jscpd -- /path/to/code

# Nix — install permanently
nix profile install github:kucherenko/jscpd

# Homebrew (macOS/Linux)
brew install jscpd

Prebuilt binaries for: macOS arm64/x64, Linux arm64/x64 (glibc + musl), Windows x64.

Quick Start

jscpd .                                       # scan current directory
jscpd ./src ./lib                             # scan specific paths
jscpd . --min-tokens 30 --min-lines 3         # tune detection sensitivity
jscpd . --blame --reporters console-full      # git blame, side-by-side authors
jscpd . --reporters json,html                 # write report files
jscpd . --threshold 10                        # fail CI if >10% duplicated
jscpd --list                                  # list all supported formats

Options

| Flag | Short | Default | Description | |------|-------|---------|-------------| | --min-tokens | -k | 50 | Minimum tokens in a clone | | --min-lines | -l | 5 | Minimum lines in a clone | | --max-lines | -x | — | Maximum lines per duplicate block | | --max-size | -z | — | Skip files larger than SIZE (e.g. 1mb) | | --mode | -m | mild | Detection mode: mild, weak, strict | | --skip-comments | — | — | Alias for --mode weak | | --format | -f | all | Comma-separated formats to check | | --ignore-pattern | -i | — | Glob patterns to ignore | | --reporters | -r | console | Comma-separated reporters | | --output | -o | report | Output directory for file reporters | | --config | -c | — | Path to .jscpd.json config file | | --threshold | -t | — | Max duplication % before exit 1 | | --blame | -b | — | Enrich clones with git blame data | | --workers | — | auto | Worker threads for parallel scan | | --skip-local | — | — | Skip clones within the same directory | | --absolute | -a | — | Use absolute paths in reports | | --silent | -s | — | Suppress console output | | --list | — | — | List all supported formats and exit |

Full options: docs/rust.md.

Reporters

| Reporter | Output | |----------|--------| | console | Clone list + statistics table (default) | | console-full | Source snippets; with --blame shows side-by-side author comparison | | json | report/jscpd-report.json | | html | report/jscpd-report.html | | sarif | report/jscpd-report.sarif (GitHub Code Scanning) | | ai | Token-efficient output for LLM pipelines | | badge | report/jscpd-badge.svg + report/jscpd-lines-badge.svg |

Also: xml, csv, markdown, xcode, threshold, silent (13 total).

Config File

Create .jscpd.json in your project root:

{
  "minTokens": 30,
  "minLines": 3,
  "format": ["javascript", "typescript", "python"],
  "ignorePattern": ["node_modules", "dist", "*.min.js"],
  "reporters": ["console", "json"],
  "output": "report",
  "threshold": 5,
  "blame": false
}

Supported Formats

223 formats including: JavaScript, TypeScript, Python, Go, Rust, Java, C/C++, C#, Ruby, PHP, Swift, Kotlin, Scala, Vue SFC, Svelte, Astro, Markdown, SQL, HTML, CSS, Bash, Dart, Lua, R, Haskell, Clojure, Elixir, Apex, CFML, and 200+ more.

Run jscpd --list for the full list, or see FORMATS.md.

Cross-format detection: Vue SFC (.vue), Svelte (.svelte), Astro (.astro), and Markdown files are tokenized per-block, enabling duplicate detection across file types.

CI

GitHub Action — installs the Rust engine, runs detection, uploads SARIF to GitHub Code Scanning:

- uses: kucherenko/jscpd@master
  with:
    threshold: 5

Pre-commit hook (Husky):

echo 'npx jscpd --threshold 5 --reporters console,silent .' > .husky/pre-commit

Full CI/pre-commit guide: docs/ci-and-hooks.md.

Programmatic Usage (Rust)

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);

Differences from jscpd v4

| Feature | jscpd v4 (Node.js) | jscpd v5 (Rust) | |---------|--------------------|-----------------| | --store (LevelDB/Redis) | Persistent store for large repos | Not supported | | Programming API | jscpd() Promise, detectClones() | Rust crate API; no Node.js API | | --reporters | All v4 reporters | All except full (use console-full) | | Output filenames | jscpd-report.json, html/ dir | jscpd-report.* prefix |

Full differences: docs/rust.md.

Architecture

jscpd (CLI binary)
 ├── cpd-core      — Detection algorithm (Rabin-Karp rolling hash)
 ├── cpd-tokenizer — Language tokenization (223 formats)
 ├── cpd-finder    — File walking, orchestration, git blame
 └── cpd-reporter  — Output formatting (13 reporters)

Links

• Homepage
• Documentation
• FORMATS.md — all 223 formats
• Performance comparison
• AI reporter, MCP server
• GitHub
• Changelog

License

MIT