dcd

dcd is a free duplicate-code detector for repository scans, best suited to developers who want adjustable matching and output they can use in review or CI. Its main trade-off is straightforward: useful depth for Linux and macOS teams, but no native Windows support in release 1.1.0.

Overview

dcd compares code using a text-based clone-detection method and supports language-aware parsing through scc for more than 250 languages. That breadth makes it relevant to projects spanning many programming languages, while the text-based approach is a better fit for teams looking for repeated code than for a general-purpose static analysis tool.

The project is free under the GNU Affero General Public License 3.0 and can be installed with Go 1.19 or newer. It is self-hosted, with repository scanning and CI integration, but no IDE integration. Commercial users can also buy a year of priority direct email support from the developer; the price is custom pricing.

Key features

dcd offers several controls for matching code that has changed rather than simply copied. The --fuzz option uses simhash distance to compare similar, non-identical lines, with values from 0 to 255. Teams can tune how much variation to accept, though that flexibility requires choosing a threshold that fits the codebase.

--gap-tolerance bridges inserted, deleted, or modified lines within otherwise matching blocks, while --max-hole-size allows modified lines inside a duplicate diagonal match. These settings are useful when edits obscure copied code; they also make dcd a more configurable choice than a tool limited to strict matches. For a focused investigation, --file compares one file with the rest of the codebase.

For visual review, dcd generates PBM scatter plots and self-contained interactive HTML reports with file heatmaps and scatter plots. The --format json option produces structured output for other tools and CI pipelines, which makes it practical to incorporate duplicate checks into automated workflows. Ignore files follow .gitignore syntax, and marked code blocks can also be excluded to keep unwanted sections out of comparisons.

Pricing

The core tool has no paid tier or usage quota stated. The support option is separate from the free software, and its price is custom pricing.

Platforms

dcd supports Linux and macOS. Release 1.1.0 removed Windows support for full filesystem compatibility and directs Windows users to WSL, so organizations requiring a native Windows application should choose another tool.

Who it's for

dcd suits developers and engineering teams that want repository-level duplicate detection, control over near-match behavior, and reports that can feed CI or other tools. Its free, self-hosted model is especially practical for teams comfortable installing software with Go and operating within the AGPL-3.0 license. It is less suitable for users who depend on IDE integration or need native Windows support.

Pros and cons

• Pros: Fuzzy matching, gap tolerance, and hole tolerance provide several ways to find duplication despite edits.
• Pros: JSON output and CI integration suit automated checks, while interactive HTML and PBM reports support visual inspection.
• Pros: Free use and parsing coverage for 250+ languages make it a broadly applicable option for Linux and macOS repositories.
• Cons: Windows users are directed to WSL rather than supported natively.
• Cons: There is no IDE integration, so developers seeking duplication feedback inside an editor will need another workflow.
• Cons: The AGPL-3.0 license may not fit every organization’s licensing requirements.

Alternatives

Code Clone Detection Tools is the broader category directory for comparing options. Consider Duplo if Windows support and prebuilt binaries for Alpine Linux, macOS, and Windows matter more than dcd's stated feature set. PMD is another free option, distributed as a downloadable static code analyzer under a BSD-style license. NiCad may suit readers who prefer MIT-licensed software and can meet its OpenTxl 11 or later requirement.

Algo VPN, CloneWorks, jscpd, Simian Similarity Analyzer, and CCFinderSW are additional alternatives.

Verdict

Choose dcd if you need a free, self-hosted duplicate-code detector for Linux or macOS and value adjustable near-match detection, visual reports, and CI-ready JSON. Look elsewhere if you require native Windows support, IDE integration, or a license other than AGPL-3.0.