JPlag vs Noplag Engine

JPlag is free software for finding pairwise similarities among programs that may indicate source-code plagiarism or collusion. It examines programming-language syntax and program structure, helping identify overlap even when code has been partly obfuscated. Analysis runs locally on the user’s machine, and the project says no data is sent externally. Comparisons are between submitted programs rather than internet sources. Listed language support includes Java, C, C++, C#, Python, JavaScript, TypeScript, Go, Kotlin, R, Rust, Swift, Scala, LLVM IR, Scheme, EMF, SCXML, text, and multi-language submissions, with varying maturity. Users can run the command-line interface or Java API, launch a report viewer from the CLI, or add JPlag through Maven Central. Reports show at most 2,500 pairs by default, adjustable with the -n option. Lower minimum matching-token lengths increase sensitivity but can also increase false positives. Running or building requires Java SE 25.

Noplag Engine is an open-source plagiarism detection tool that checks text for verbatim and near-verbatim matches against a corpus you control. It uses winnowing fingerprints to find candidate sources, then aligns matching character ranges. Reports show similarity by source, passage offsets, and coverage accounting. It accepts.txt,.md,.pdf, and.docx files, with folder ingestion and HTTP uploads, and exposes a /v1 API for checks, reports, uploads, progress events, and corpus management. The API ships without authentication. The open-source engine searches a local corpus; the hosted product also searches the live web. It does not detect paraphrase, semantic similarity, or AI-written text. The engine can run on your own hardware with Docker Compose under the Apache 2.0 license. The repository lists Python 3.12 or newer for development and PostgreSQL in its Docker Compose setup. The free hosted plan costs nothing and allows 3 checks per month, while self-hosting permits unlimited local checks. Pro costs $9.99 a month and Premium costs $19.99 a month; Enterprise pricing is custom.