QuickDup

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What QuickDup is

QuickDup is a repository code clone detector for finding structurally similar code patterns. It fingerprints changes in indentation and the first word on each line, skips comments and blank lines, and does not parse abstract syntax trees. Its normalized-indent, word-indent, word-only, and inlineable strategies provide different ways to identify candidates. QuickDup tokenizes source lines and applies Jaccard similarity filtering, with a default threshold of 75%. The README lists comment-prefix support for languages including Go, C and C++, Java, JavaScript, TypeScript, C#, Python, Ruby, SQL, Lua, and MATLAB. Results are saved as machine-readable JSON in a .quickdup directory. For pull requests, it can emit GitHub Actions annotations and restrict them to files changed against a Git reference. Incremental parsed-file caching is available for word-indent; other listed strategies re-parse files on each run. QuickDup is free and open source under the MIT License, with installation options for Linux, macOS, and Windows, as well as installation from source with Go. The README reports processing about 100,000 lines in about 500 ms on 8 cores. It is intended to surface candidates for AI-assisted review; an AI agent and human reviewer verify them.

Who it suits

QuickDup suits software teams that want to surface possible code clones across a repository and review them with an AI agent and a human decision maker. It may also suit teams using GitHub Actions annotations as part of pull request review.

What it does well

Free and open source under the MIT License.
Offers four detection strategies.
Supports repository scans on Linux, macOS, and Windows.
Can annotate pull requests through GitHub Actions.
Writes scan results as machine-readable JSON.

What to know first

Heuristic results can include false positives.
May miss semantic duplicates with different structure.
Incremental parsed-file caching is limited to word-indent.
No IDE integration is listed.

Limits

QuickDup generates candidates rather than confirming duplication, and can produce false positives or miss semantic duplicates with different structure. Incremental parsed-file caching works only with the word-indent strategy; the other listed strategies re-parse files on each run.

Getting started

Open the QuickDup GitHub repository.
Choose the installer for Linux or macOS, use the PowerShell installer on Windows, or install from source with Go.
Run QuickDup against a repository.
Review the machine-readable JSON results in the .quickdup directory.
Optionally configure GitHub Actions annotations for pull request comments.

Verdict

Choose QuickDup if you want a free, open source way to generate structural code clone candidates for review, including GitHub Actions annotations. Look elsewhere if you need definitive duplicate detection: its heuristic results can include false positives and miss differently structured semantic duplicates.

Questions

Is QuickDup free?

Yes. QuickDup is free and open source under the MIT License.

Which platforms does QuickDup support?

Linux, macOS, and Windows.

Which programming languages does it support?

The README lists comment-prefix detection for languages including Go, C and C++, Java, JavaScript, TypeScript, C#, Python, Ruby, SQL, Lua, and MATLAB.

Does QuickDup integrate with GitHub Actions?

Yes. It can emit annotations for inline pull request comments and limit them to files changed against a Git reference.

Does QuickDup parse abstract syntax trees?

No. It fingerprints indentation changes and the first word on each line without AST parsing.

Who makes QuickDup?

The repository is under the Asynkron GitHub organization. The organization profile lists Stockholm, Sweden.

Facts from QuickDup's own pages

Caching: Incremental caching is available only for the word-indent strategy; the other listed strategies re-parse files on each run. · github.com, 4 Oct 2026
Caching limit: Incremental parsed-file caching is supported only by the word-indent strategy; the other listed strategies re-parse files on each run. · github.com, 5 Oct 2026
Detection approach: QuickDup fingerprints indentation changes and the first word on each line, and does not use AST parsing. · github.com, 4 Oct 2026
Detection strategies: It offers normalized-indent, word-indent, word-only, and inlineable detection strategies. · github.com, 5 Oct 2026
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. · github.com, 5 Oct 2026
GitHub integration: QuickDup can emit GitHub Actions annotations for inline pull request comments and limit annotations to files changed against a Git reference. · github.com, 4 Oct 2026
Headquarters: Huddinge, Sweden · github.com, 28 Sept 2026
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. · github.com, 5 Oct 2026
Installation: The README provides installer commands for Linux and macOS, a PowerShell installer for Windows, and installation from source with Go. · github.com, 4 Oct 2026
Intended use: It is designed to generate candidate duplicates for AI-assisted code review, with an AI agent and human decision maker verifying candidates. · github.com, 4 Oct 2026
Languages: The README lists comment-prefix support for languages including Go, C/C++, Java, JavaScript/TypeScript, C#, Python, Ruby, SQL, Lua, and others. · github.com, 5 Oct 2026
Language support: The README lists comment-prefix detection for languages including Go, C#, JavaScript, TypeScript, Python, Ruby, SQL, Lua, and MATLAB, among others. · github.com, 4 Oct 2026
License: QuickDup is released under the MIT License. · github.com, 5 Oct 2026
Limitations: The project describes QuickDup as a heuristic candidate generator that can produce false positives and miss semantically duplicate code with different structure. · github.com, 5 Oct 2026
Maker location: The maker's GitHub organization profile lists Stockholm, Sweden. · github.com, 5 Oct 2026
Output: Results are written as machine-readable JSON files in a .quickdup directory. · github.com, 5 Oct 2026
Performance: The README reports scanning about 100,000 lines of code in about 500 ms on 8 cores. · github.com, 5 Oct 2026
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. · github.com, 5 Oct 2026
Release: The GitHub releases page lists v0.6.0 as the latest release. · github.com, 5 Oct 2026
Similarity filtering: QuickDup tokenizes source lines, computes Jaccard similarity, and filters patterns below a default similarity threshold of 75%. · github.com, 5 Oct 2026

Where QuickDup stands on Freedom251

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