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QuickDup

github.com

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Spec score 6.9 #20 of 23 in Code Clone Detection Tools

What it is

QuickDup is a repository code clone detector that finds candidate duplicate patterns using changes in indentation and the first word on each line. It skips comments and blank lines, tokenizes source lines and uses Jaccard similarity to filter patterns below a default 75% threshold. It does not parse abstract syntax trees. Detection options include normalized-indent, word-indent, word-only and inlineable strategies. The README lists comment-prefix detection for languages including Go, C and C++, Java, JavaScript and TypeScript, C#, Python, Ruby, SQL, Lua and MATLAB. QuickDup can emit GitHub Actions annotations for inline pull request comments and restrict them to files changed against a Git reference. Results are written as machine-readable JSON in a .quickdup directory. Incremental caching is available only for the word-indent strategy; other listed strategies re-parse files on each run. The README reports processing about 100,000 lines in about 500 ms on 8 cores. QuickDup is free under the MIT License, with installers for Linux, macOS and Windows, or installation from source with Go.

Spec sheet

Purpose
QuickDup is a structural code clone detector that finds duplicate code patterns using indent-delta fingerprinting and is designed to generate candidates for AI-assisted code review.Read 5 Oct 2026 · github.com
License
QuickDup is released under the MIT License.Read 5 Oct 2026 · github.com
Headquarters
Huddinge, SwedenRead 28 Sep 2026 · github.com
Caching
Incremental caching is available only for the word-indent strategy; the other listed strategies re-parse files on each run.Read 4 Oct 2026 · github.com
Caching limit
Incremental parsed-file caching is supported only by the word-indent strategy; the other listed strategies re-parse files on each run.Read 5 Oct 2026 · github.com
Detection approach
QuickDup fingerprints indentation changes and the first word on each line, and does not use AST parsing.Read 4 Oct 2026 · github.com
Detection strategies
It offers normalized-indent, word-indent, word-only, and inlineable detection strategies.Read 5 Oct 2026 · github.com
GitHub Actions integration
It can emit GitHub Actions annotations for inline pull request comments and can limit annotations to files changed against a Git reference.Read 5 Oct 2026 · github.com
GitHub integration
QuickDup can emit GitHub Actions annotations for inline pull request comments and limit annotations to files changed against a Git reference.Read 4 Oct 2026 · github.com
How it works
It fingerprints indentation changes and the first word on each line, skips comments and blank lines, and detects patterns without AST parsing.Read 5 Oct 2026 · github.com
Installation
The README provides installer commands for Linux and macOS, a PowerShell installer for Windows, and installation from source with Go.Read 4 Oct 2026 · github.com
Intended use
It is designed to generate candidate duplicates for AI-assisted code review, with an AI agent and human decision maker verifying candidates.Read 4 Oct 2026 · github.com
Language support
The README lists comment-prefix detection for languages including Go, C#, JavaScript, TypeScript, Python, Ruby, SQL, Lua, and MATLAB, among others.Read 4 Oct 2026 · github.com
Languages
The README lists comment-prefix support for languages including Go, C/C++, Java, JavaScript/TypeScript, C#, Python, Ruby, SQL, Lua, and others.Read 5 Oct 2026 · github.com
Limitations
The project describes QuickDup as a heuristic candidate generator that can produce false positives and miss semantically duplicate code with different structure.Read 5 Oct 2026 · github.com
Maker location
The maker's GitHub organization profile lists Stockholm, Sweden.Read 5 Oct 2026 · github.com
Output
Results are written as machine-readable JSON files in a .quickdup directory.Read 5 Oct 2026 · github.com
Performance
The README reports scanning about 100,000 lines of code in about 500 ms on 8 cores.Read 5 Oct 2026 · github.com
Release
The GitHub releases page lists v0.6.0 as the latest release.Read 5 Oct 2026 · github.com
Similarity filtering
QuickDup tokenizes source lines, computes Jaccard similarity, and filters patterns below a default similarity threshold of 75%.Read 5 Oct 2026 · github.com

Strong points and limits

Strong points

  • Offers four listed detection strategies.
  • Can add GitHub Actions pull request annotations.
  • Writes machine-readable JSON scan results.
  • Free and licensed under MIT.
  • Installers cover Linux, macOS and Windows.

Limits

  • Heuristic detection can produce false positives.
  • May miss semantic duplicates with different structure.
  • Incremental caching is limited to word-indent.
  • No IDE integration is listed.

Who it suits

It suits developers and teams seeking candidate duplicates in a repository, especially those using GitHub Actions or AI-assisted code review. A human reviewer and AI agent are expected to verify candidate matches.

Verdict

QuickDup makes its fingerprinting approach, outputs and caching limit explicit. It is a candidate finder, not a definitive judge of whether two pieces of code are duplicates.

Where Specifiction places it

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