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JPlag

Free#6 of 18 in Code Duplication Detection Tools

JPlag: A free, syntax-aware tool for pairwise program-similarity analysis across 20 languages. Ranked #6 of 18 in Code Duplication Detection Tools by our editors (6.7/10); pricing: Free plan; best for academic or multi-language similarity analysis.

6.7/10Editor score

Visit JPlag

JPlag6.7 Visit JPlag

At a glance

Editor score
6.7 / 10
Pricing
Free plan
Best for
Academic or multi-language similarity analysis
Free plan
Yes
Paid from
Free
Near-duplicate detection
Yes
Founded
1996
Facts checked
27 Sep 2026

Where it wins
- Syntax-aware matching across 20 supported languages
- Handles some obfuscation and code modifications
- Free, open source, with CLI and Java API access
Where it doesn't
- Focused on pairwise analysis rather than duplication gates
- No CI pull-request reporting or trend visualisation
- Self-hosted setup relies on community support

Our verdict on JPlag

JPlag is a free, open-source tool that compares programs pairwise to identify source-code similarity. It is primarily suited to programming education, where instructors review student submissions, and it can also help examine duplicated software modules. Analysis runs locally on Windows, macOS, Linux, or a self-hosted environment, with source code and results kept on the local system. JPlag supports 20 programming and modeling languages and produces a report for local viewing.

Its analysis is syntax- and structure-aware rather than limited to literal text matching. The published features include detection of similarities that persist through some obfuscation or code modifications, exclusion of common starter or template code, comparisons with prior cohorts, and configurable minimum matching-token sensitivity. Results include pairwise similarity values that can be exported as CSV. Users can run JPlag through its command-line interface, integrate it through a Java API, or connect it with Maven for Java-project workflows.

JPlag fits teams that want a local, transparent comparison tool for coursework or focused similarity investigations without a hosted subscription. Its scope is narrower than platforms built around continuous engineering workflows: the category specifications show no CI pull-request reporting, duplication gates, or trend visualisation. Community support is the listed support channel, and deployment is self-hosted. Choose JPlag when pairwise, language-aware analysis and prior-cohort comparison are central requirements; consider another tool when automated pull-request checks, dashboard trends, or broader workflow controls are priorities.

Your product? Our editors can test JPlag in depth and publish a review, labelled as paid · from $149/mo →

JPlag pricing

Plans Free planFree Free to use — no paid tier required for the core job.

See plans on jplag.github.io

JPlag fact sheet

Free plan	Yes
Paid from	Free
Supported languages	20
Near-duplicate detection	Yes
CI/PR reporting	None
Duplication gates	No
Trend visualisation	No
Open-source option	Yes
Deployment	Self-hosted
Platforms	Windows, macOS, Linux
Support	Community
Built for	Small business, Mid-market, Enterprise (editorial estimate)
Integrations	1 integrations: Maven
Pricing	Free plan
Website	jplag.github.io
Facts checked	27 Sep 2026

JPlag integrations

JPlag lists 1 integrations on its own site.

Maven

Alternatives to JPlag

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JPlag vs the competition

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Featured on iTechGuides

JPlag is listed in our Code Duplication Detection Tools 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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Last updated 7 Oct 2026 · How we research and update