MOSS
MOSS: A free code-similarity checker for programming courses, not web or academic-document plagiarism. Ranked #5 of 31 in Plagiarism Checkers by our editors (8.8/10); pricing: Free plan; best for free source-code checks across many languages.
At a glance
- Editor score8.8 / 10
- PricingFree plan
- Best forFree source-code checks across many languages
- Free planYes
- Paid fromFree
- Web source matchingNo
- Founded1994
- Facts checked21 Sep 2026
Where it wins
- Free for non-commercial use with account registration
- Analyzes source code across 24 listed programming languages
- Highlights matching passages and excludes expected shared code
Where it doesn't
- Designed for non-commercial use
- Requires Linux submission script for file submission
- Results indicate similarity and require human review
Our verdict on MOSS
MOSS, or Measure Of Software Similarity, is an Internet service for comparing source-code submissions and detecting potential plagiarism in programming classes. It is suited to instructors and educational settings that need to review similarities across student programs. MOSS analyzes source code across 24 listed programming languages, returns HTML result pages, and shows similar program pairs with highlighted matching passages. It is free for non-commercial use, with account registration required.
Its strongest capability is focused source-code comparison rather than general plagiarism detection. Similarity percentage scores and matched-line counts help reviewers identify which submissions deserve attention, while automatic exclusion of expected shared code can remove libraries or instructor-provided code from the comparison. A Linux submission script supports the submission workflow, and the service is available through web and Linux platforms. The published results are intended to support review, not replace it: similarity is not proof of plagiarism, and the vendor emphasizes the need for human judgment.
MOSS is a practical choice for programming courses that need free comparisons across multiple languages and clear HTML reporting. It is less suitable for checking webpages, essays, or academic documents because its scope is source-code similarity analysis. The service is also limited to non-commercial use, and its workflow centers on account access and the Linux submission script. Choose MOSS when code comparison, matching-line detail, and expected-code exclusion matter most; choose another category of checker when the goal is web or academic-document plagiarism detection.
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MOSS pricing
MOSS fact sheet
| Free plan | Yes |
|---|---|
| Paid from | Free |
| Web source matching | No |
| Academic source matching | No |
| Supported languages | 24 languages |
| Word limit | Not verified |
| Report export formats | HTML |
| API access | Not verified |
| LMS integration | Not verified |
| Deployment | Cloud |
| Platforms | Web, Linux |
| Support | |
| Built for | Small business, Mid-market, Enterprise (editorial estimate) |
| Pricing | Free plan (source) |
| Website | theory.stanford.edu |
| Facts checked | 21 Sep 2026 |
Alternatives to MOSS
- Turnitin AI Writing DetectionA focused institutional tool for identifying text that may be AI-generated or modified.9.4
- Crossref Similarity CheckA focused manuscript-screening service with academic matching, reports, filters, and API access.9.2
- iThenticateA paid similarity checker built for researchers, publishers, and private repositories.9.0
MOSS vs the competition
- MOSS vs Turnitin AI Writing Detection
- MOSS vs Crossref Similarity Check
- MOSS vs iThenticate
- MOSS vs Copyscape
- MOSS vs StrikePlagiarism
- MOSS vs DrillBit
Compare MOSS with any tool side by side →
Also Ranked In
MOSS is ranked in 2 of our directories.
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Featured on iTechGuides
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Reviewed by iTechGuides Editors · Editorial team · Updated Oct 2026
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