JPlag
JPlag: A free, local code-similarity checker for instructors reviewing programming submissions. Ranked #23 of 28 in Plagiarism Detection Software by our editors (6.8/10); pricing: Free plan; best for instructors needing private, structure-aware code checks.
At a glance
- Editor score6.8 / 10
- PricingFree plan
- Best forInstructors needing private, structure-aware code checks
- Free planYes
- Paid fromFree
- AI detectionNo
- Founded1996
- Facts checked23 Sep 2026
Where it wins
- Compares code by syntax and structure, not just text similarity
- Runs locally and can exclude starter code or compare past cohorts
- Offers CLI, Java API, report viewing and CSV export
Where it doesn't
- Does not compare submissions against the internet
- No LMS integration or AI detection
- Support is community-based
Our verdict on JPlag
JPlag is an open-source tool for finding pairwise similarities among program submissions, commonly used to check student programming assignments for copying or collusion. It compares code with awareness of programming-language syntax and structure rather than searching the internet. Instructors and institutions can run analysis locally through a command-line interface or Java API, then inspect results in a report interface. Its focus is code submissions, so it suits programming courses better than teams seeking a general-purpose plagiarism checker.
The local workflow is a central fit consideration: code and results do not need to be uploaded for analysis. JPlag can exclude common starter or base code, compare a current cohort with previous cohorts, and let users adjust match sensitivity through minimum-token settings. Match merging is intended to counteract obfuscation attempts. Pairwise similarity values can also be exported as CSV. These options give instructors ways to interpret similarities in the context of shared assignment scaffolding and earlier submissions, while keeping the analysis centered on code structure.
JPlag is distributed as a free open-source project rather than a commercial paid service, and it provides a CLI and Java API for integrating analysis into local workflows. Its boundaries matter: it does not compare assignments against internet sources, has no LMS integration, and does not offer AI detection. Support is community-based. Choose it when the task is private, structure-aware comparison of programming work and local or API-driven analysis fits; choose another product if internet-wide checking, LMS integration, or AI detection is essential.
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JPlag pricing
JPlag fact sheet
| Free plan | Yes |
|---|---|
| Paid from | Free |
| AI detection | No |
| LMS integrations | No |
| API access | Yes |
| Browser extension | No |
| Supported languages | Not verified |
| Maximum check size | Not verified |
| Deployment | Self-hosted |
| Platforms | Windows, macOS, Linux |
| Support | Community |
| Built for | Small business, Mid-market, Enterprise (editorial estimate) |
| Pricing | Free plan |
| Website | github.com |
| Facts checked | 23 Sep 2026 |
Alternatives to JPlag
- Turnitin SimilarityA comprehensive academic similarity checker with LMS workflows and advanced match flags.9.3
- DrillBitBroad academic and classroom checks with one-time page-credit pricing.9.1
- iThenticateA scholarly similarity checker with deep academic coverage and flexible organizational integrations.8.9
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Featured on iTechGuides
JPlag is listed in our Plagiarism Detection Software directory. Add the badge to your site — it links back to this page.
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Reviewed by iTechGuides Editors · Editorial team · Updated Oct 2026
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