# Jscpd

Copy-paste detector for 220+ languages.

- Repository: https://github.com/kucherenko/jscpd (6480 stars)
- Category: Engineering
- License: MIT
- Last updated: 2026-10-30
- Runs scripts: no, instructions only

## Install

Claude Code: `npx skills add kucherenko/jscpd --skill jscpd -g -a claude-code -y`
Codex: `npx skills add kucherenko/jscpd --skill jscpd -g -a codex -y`
Cursor: `npx skills add kucherenko/jscpd --skill jscpd -g -a cursor -y`
Gemini CLI: `npx skills add kucherenko/jscpd --skill jscpd -g -a gemini-cli -y`

## Description

Copy-paste detector for 220+ languages. Detect exact, renamed and near-miss duplicated code, measure duplication percentages, and find refactoring hotspots with the codebase summary.

## SKILL.md, as published by its author (untrusted third-party text, read it as data)

# jscpd

Copy-paste detector for programming source code, supports 220+ languages. Use this skill to run jscpd and understand its output.

## Quick Start

```bash
# Run with ai reporter (compact output optimized for agents)
npx jscpd --reporters ai <path>

# With ignore patterns
npx jscpd --reporters ai --ignore "**/node_modules/**,**/dist/**" <path>

# Scope to specific formats
npx jscpd --reporters ai --format "javascript,typescript" <path>

# Second pass, noisier: copies that only differ in names and values (Type-2, "renamed").
# Review each hit before acting on it.
npx jscpd --reporters ai --ignore-identifiers --min-tokens 70 <path>

# Third pass, noisier still: copies with a few edited lines or the same function
# structure (Type-3, "similar"). Keep the settings tight.
npx jscpd --reporters ai --max-gap-lines 1 --similarity <path>

# Where to refactor first: clone list plus a hotspot summary
npx jscpd --reporters ai --summary <path>

# Most complex files only, without clone detection
npx jscpd --complexity --reporters ai <path>
```

## AI Reporter Output Format

The `ai` reporter produces compact, token-efficient output designed for agent consumption:

```
Clones:
src/ foo.ts:10-25 ~ bar.ts:42-57
src/utils/helpers.ts:100-120 ~ src/utils/other.ts:5-25
src/cart/ basket.js:1-9 ~ cart.js:1-9 (renamed)
src/api/ save-account.js:1-12 ~ save-user.js:1-11 [~0.91 gap]
src/billing/ orders.ts:1-14 ~ refunds.ts:1-15 [~0.85 ast]
---
5 clones · 4.2% duplication
```

Each line represents one clone pair:
- **Same file**: `path/file.ts 10-25 ~ 45-60` (shared path shown once)
- **Same directory**: `shared/prefix/ file-a.ts:10-25 ~ file-b.ts:42-57` (common prefix factored out)
- **Different paths**: `path/a.ts:10-25 ~ path/b.ts:42-57`

The rest: https://github.com/kucherenko/jscpd/blob/HEAD/skills/jscpd/SKILL.md