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Tech riderRev. 29 Sept 2026

Duplo

Ch 017.3of 23 Code Clone Detection Tools
  1. 1Runs onLinux, Mac, Windows
  2. 2CostsFree plan
  3. 3Clone detection methodtext
  4. 4Scan scoperepository
  5. 5CI integrationYes
  6. 6Self-hosted optionYes
6 lines stated Written from the maker's own pages: github.com
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Overview

Duplo is ranked #1 of 23 in code clone detection tools on Specifiction. It runs on Linux, macOS, Windows. There is a free plan.

Duplo plans and pricing

All plans
Duplo Free Free software under GNU GPL v2 or later · prebuilt binaries for Alpine Linux, macOS and Windows github.com · 29 Sept 2026

Compared on code clone detection tools

Free plan
Yesgithub.com
Clone detection method
textgithub.com
Scan scope
repositorygithub.com
CI integration
Yesgithub.com
Self-hosted option
Yesgithub.com

Facts

Purpose
Duplo finds duplicated source code blocks in large codebases.github.com · 28 Sept 2026
Language support
It has built in support for C/C++, Java, C#, VB, GCC assembly, Ada, Erlang, TypeScript and Swift, and can also scan arbitrary text files.github.com · 28 Sept 2026
Filtering
For supported languages, Duplo can remove comments, preprocessor directives and other syntax before checking for duplicate code.github.com · 28 Sept 2026
Reports
It can produce JSON and XML output as well as text reports.github.com · 28 Sept 2026
GitHub Actions
The maker links a GitHub Action that can fail a build when duplicate blocks are found.github.com · 28 Sept 2026
Action limits
The linked GitHub Action has configurable minimum duplicate lines and minimum line length, and a maximum number of files to report.github.com · 28 Sept 2026
Performance
The README reports processing Quake2's 266 files and 102,740 lines in 9 seconds on modern hardware in 2025, and says multithreading can improve performance almost linearly.github.com · 28 Sept 2026
Downloads
Pre-built binaries are available for Alpine Linux, macOS and Windows, and the project can also be built from source.github.com · 28 Sept 2026
Support
The README directs users to open an issue for feedback, feature requests and bug reports.github.com · 28 Sept 2026
License
Duplo is free software under GNU GPL version 2 or, at the user's option, any later version.github.com · 28 Sept 2026
Caveat
The license section says Duplo is provided without warranty, including implied warranties of merchantability or fitness for a particular purpose.github.com · 28 Sept 2026
Text files
Duplo can detect duplicates in arbitrary text files, including duplicates within a single file.github.com · 29 Sept 2026
Input
Files can be supplied through standard input or a separate file containing the file list.github.com · 29 Sept 2026
Limit
The README's quick-start example requires at least 20 lines for a duplicate, though command-line options can be adjusted.github.com · 29 Sept 2026
Maintainer
Duplo was originally developed by Christian M. Ammann and is now maintained and developed by Daniel Lidström.github.com · 29 Sept 2026

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Where it ranks on Specifiction

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Sources