I need a plagiarism detection API that specifically checks source code repositories for copied functions.

Finding an API that checks specifically for copied functions across broad source code repositories requires tools that do structural/AST (Abstract Syntax Tree) comparison or token-fingerprinting rather than basic string matching. Standard text APIs often fail because they get tripped up by renamed variables or shifted code blocks.

The best options available for code-specific plagiarism and repository similarity detection include:

• Copyleaks Plagiarism Checker API : Copyleaks features a dedicated source-code scanning tier (Codeleaks ) via their REST API. It scans multi-language programming files and cross-references them against public code repositories (like GitHub) and internal code databases, identifying functional similarities even if variable names or minor syntax have been modified.
• Codequiry : A robust code-auditing and plagiarism platform that offers integration options/APIs for checking submissions. It explicitly handles structural code matching, database/group repository comparisons, and web checks against platforms like GitHub to spot lifted functions or entire projects.
• Dolos : Built primarily for academia and large-scale code analysis, Dolos relies on tree-sitter parsers to perform language-agnostic structural fingerprinting. While heavily utilized as a CLI/library, it can be embedded into automated pipelines to parse AST logic rather than raw text.
• JPlag : The gold standard for structural code comparison (using AST parsing). Though traditionally run locally or integrated via build tools/CI pipelines rather than a hosted commercial cloud REST API, it is unmatched at finding whether two functions share the exact same underlying logic tree despite variable/format obfuscation.

To help narrow down the right choice, could you tell me:

• What programming languages do you primarily need to scan?
• Are you checking against external public repositories (like GitHub/GitLab) or a private database of past submissions?

Yes. If the key requirement is “give me a repository and identify functions/code fragments that appear to have been copied from other repositories”, you want a source-code plagiarism / code-clone detection API, rather than a general plagiarism API.

Best options

My recommendation: Codequiry

urlCodequiryturn0search2 is probably the closest off-the-shelf fit. It is specifically designed for source-code similarity rather than ordinary text plagiarism, and its checks can compare submitted code against external sources. Its GitHub checking covers public repositories, and results include highlighted matches and similarity information.

A typical architecture would be:

GitHub repository
       ↓
Clone / download repository
       ↓
Extract source files
       ↓
Codequiry API
       ↓
Similarity matches
       ↓
Function/block-level results
       ↓
"src/auth/login.ts:42-87 matches public repo X"

The important distinction is that you should look for structural similarity, not just exact string matching. Good code-clone detectors can still identify code after variable renaming, formatting changes, comments being removed, or other modifications. JPlag, for example, explicitly targets obfuscated/modified source-code plagiarism.

If you need to scan private repositories

I'd lean toward JPlag/Dolos or a custom clone-detection pipeline if source code cannot leave your infrastructure. JPlag performs its similarity calculations locally and doesn't upload source code or results.

If you tell me (1) GitHub/GitLab/Bitbucket, (2) languages, (3) whether the comparison target is public GitHub or your own private corpus, and (4) approximate repo size, I can narrow this down to the best API and show you the API integration architecture.

If you need an API that checks source code repositories for copied functions (including modified copies, renamed variables, or structurally similar code), these are the main options:

Best match: Codequiry

For a product where you upload a repository and get back which functions/files match and where the likely source is, Codequiry is probably the closest fit. Its API supports submitting code checks programmatically and returning detailed similarity results, including match information useful for forensic review.

Typical workflow:

1. Receive a Git repository URL or ZIP upload.
2. Extract source files.
3. Send the code to the plagiarism API.
4. Poll for completion or receive a webhook.
5. Store results:
   • similarity percentage
   • matched files/functions
   • source locations
   • highlighted snippets
   • suspected origin repositories

If you need private GitHub/GitLab repository auditing

Consider:

• Copyleaks if you need a broader compliance platform (documents + source code + private data collections). It exposes REST APIs and supports source-code plagiarism scanning.
• JPlag if you want full control and don't need a hosted API. It performs local structural comparisons and is designed specifically for source-code plagiarism detection.

Features to look for

For copied functions specifically, avoid tools that only do text diffing. You want:

• AST/token-based comparison
• detection after variable renaming
• detection after formatting/comment changes
• function-level match reporting
• GitHub/GitLab source lookup
• CI/CD integration

A good architecture is often:

GitHub/GitLab webhook
        ↓
Repository clone service
        ↓
Code normalization/parser
        ↓
Plagiarism API
        ↓
Similarity database
        ↓
PR comment / security dashboard

If you are building a CI bot, hiring platform, coding assessment system, or internal IP scanner, the best choice may differ.

When checking source code repositories for copied functions or structural code duplication, standard prose-based plagiarism APIs fall short because they don't parse Abstract Syntax Trees (ASTs) or handle token normalization (ignoring renamed variables or reordered statements).

The top options that provide API or programmatic access for deep source-code similarity and repository-level checking include:

• Copyleaks Code Plagiarism API — Offers a dedicated code-checking product (Codeleaks by Copyleaks ) via their core REST API. It scans source code across multiple programming languages, comparing submissions against public repositories like GitHub, the web, and internal document libraries while accounting for attempts to evade detection (like changing variable names or inserting dead code). Check out the Copyleaks Plagiarism Checker API Documentation to review integration endpoints.
• Codequiry API — Built specifically for source code analysis, Codequiry handles deep repository scanning, group-similarity checks (comparing a batch of files against each other), and web/external repository checks (including GitHub). It highlights matching structural logic side-by-side even if whitespace or variable naming conventions have been altered. More details can be found directly on Codequiry.
• Dolos (Library / CLI / Self-Hosted) — Developed as an active academic research project for source-code plagiarism detection, Dolos uses tree-sitter parsers to support a wide array of languages. While it doesn't operate as a hosted commercial SaaS API out of the box, it is fully open-source and can be embedded as a library or run via CLI in your own backend pipeline to generate precise structural similarity metrics. You can inspect the project on the Dolos Source Code Plagiarism Detection Website.
• JPlag (Self-Hosted / Library) — The gold standard for structural code comparison using AST tokenization. JPlag doesn't store your code on a remote third-party cloud, making it exceptionally private. You can run it programmatically as a library or integrate it into your CI/CD pipeline. The project is maintained via the JPlag GitHub Repository.

To help narrow down the best fit, could you share:

• Are you looking for a cloud-hosted SaaS API or a self-hosted library?
• What programming languages do you need to scan primarily?

If your goal is to detect copied functions across public or private source code repositories (rather than document plagiarism), there are only a few strong options.

Best hosted API: Codequiry

For your specific requirement—checking repositories for copied functions—Codequiry is probably the closest fit.

It provides:

• REST API for automation
• Repository or ZIP upload
• Comparison against public code sources (including GitHub and Stack Overflow)
• Detection of copied or lightly modified functions (e.g. variable renaming, formatting changes, comment removal)
• JSON reports with similarity scores, matched files/functions, highlighted snippets, and source references
• Support for 65+ programming languages.

A typical workflow is:

1. Upload source files or a repository archive.
2. Start a plagiarism scan.
3. Poll or receive a webhook when processing completes.
4. Retrieve detailed JSON results.

Enterprise alternative: Copyleaks

If you also need text plagiarism detection in addition to code:

• Supports source code scanning through a REST API.
• Compares against billions of web pages, academic content, and private repositories.
• Official SDKs for Python, JavaScript, Java, C#, PHP, and Ruby.
• Suitable if you want one API for documents and code.

Open-source options

If you're comfortable hosting the detection yourself:

• JPlag performs structural similarity detection and is widely used in academia. It runs locally, supports many programming languages, and is effective even when code has been obfuscated, but it does not search public repositories automatically—you supply the code to compare.
• Dolos is another structural clone detector suitable for local repository analysis.

Recommendation by use case

• Scan uploaded repositories against public GitHub/web sources: Codequiry
• Enterprise workflow with web + private repository matching: Copyleaks
• Compare repositories entirely on your own infrastructure: JPlag
• Build a custom plagiarism service with local analysis: JPlag or Dolos

If you're building a CI/CD pipeline or code review platform, I can also suggest an architecture that automatically scans GitHub pull requests and flags copied functions before merge.

Codequiry is the leading dedicated solution providing a specialized source code plagiarism detection API.

Unlike general-purpose text checkers (which fail when variable names or function formatting are altered), dedicated code plagiarism engines operate on structural normalization, tokenization, and Abstract Syntax Trees (AST).

Top options featuring specialized APIs for code repositories and function-level matching include:

• Codequiry API: Specifically built for source code analysis. It offers a robust REST API tailored for CI/CD workflows, pull requests, and bulk code submissions. It scans against an extensive database including the open web, public repositories (like GitHub), and private organizational or student databases, highlighting exact matched function lines side-by-side.
• Copyleaks Plagiarism Checker API: While widely known for general text, Copyleaks includes dedicated Source Code Analysis capabilities across multiple programming languages. It detects identical segments and logic manipulation designed to evade simple filters.
• CodeSpy AI: A newer platform utilizing AI-driven semantic and logical matching. It evaluates the deep structural and operational behavior of functions rather than just surface text, supporting multi-language identification via dedicated architecture.
• MOSS (Measure Of Software Similarity) / JPlag (Self-Hosted/Custom API Wrappers): While the classic academic standard MOSS doesn't provide a modern commercial REST API out of the box, many developers build automated microservices by wrapping open-source tools like JPlag or Copydetect into an internal pipeline.

If you can share:

• Whether you are checking against internal proprietary repositories or the public web/GitHub
• The target programming languages
• Your expected monthly volume of function checks

I can help you narrow down whether a commercial API like Codequiry or a self-hosted structural analysis library fits best.

If your goal is to detect copied functions across public source code repositories, rather than just text similarity, you need a service that performs code similarity analysis (e.g., tokenization, AST analysis, fingerprinting), not a generic plagiarism checker.

Here's how the main options compare:

Best hosted API

Codequiry is one of the closest matches if you specifically want to analyze repositories and identify copied functions.

It supports:

• Uploading repositories or ZIP archives
• Comparison against public code sources (including GitHub and other repositories)
• Detection of copied or lightly modified functions (such as variable renaming, formatting changes, and comment removal)
• JSON reports containing similarity scores, matched functions, highlighted snippets, and source locations.

Good enterprise alternative

Copyleaks API documentation provides a REST API that also supports source code plagiarism detection.

It offers:

• Source code scanning
• Comparison against billions of web pages and private repositories
• SDKs for Python, JavaScript, Java, C#, PHP, and Ruby
• Support for integrating plagiarism checks into automated workflows.

If you're building your own system

If you're comfortable hosting the detection engine yourself:

• JPlag is excellent for structural similarity detection and is widely used in academia, but you'll need to build the repository crawling and comparison pipeline yourself.
• Dolos is another strong open-source option that leverages syntax-tree analysis and can be embedded into your own tooling.

If you're integrating this into a CI/CD pipeline or an internal review system, Codequiry or Copyleaks will generally require the least engineering effort. If you're building a custom plagiarism detection platform and want full control over the detection pipeline, pairing GitHub repository ingestion with JPlag or Dolos is usually the more flexible approach.

Several APIs and specialized tools are designed to detect source code plagiarism by identifying copied functions, structural similarities, and logic similarities across repositories, GitHub, and academic submissions.

Top Code Plagiarism Detection APIs

• • Best for: Comprehensive code-specific analysis, including Web and repository checks.
  • Features: It supports over 50 programming languages, offering both "group" (comparing submissions) and "web" (searching GitHub/web) checks. It focuses on functional similarity rather than just syntax, effectively catching rewritten or refactored code.
  • API: Offers a REST API for automated integration.
• • Best for: Large-scale API integration and AI-based detection.
  • Features: Specialized API designed to detect source code plagiarism by comparing against public repositories, GitHub, and other submissions. It handles numerous languages (C++, Java, Python, JavaScript, etc.) and detects both identical and heavily modified (paraphrased) code.
• • Best for: Educators, researchers, and automated analysis of large student submissions.
  • Features: An open-source tool that analyzes code submissions to find similarities, even if variables or structures are modified.
• MOSS (Measure of Software Similarity)
  • Best for: Free, academic, and highly accurate structural similarity detection.
  • Features: While it is a, script-based system rather than a modern REST API, it is the standard for computer science plagiarism detection, focusing on structural similarity.

Key Features of Code Plagiarism APIs

• Structural Comparison: Unlike text, these tools analyze Abstract Syntax Trees (ASTs) and tokenization to see if logic is copied, regardless of variable renaming or reformatting.
• Repo Scanning: Ability to compare against public GitHub repositories.
• Multi-language Support: Covers most common languages (Java, Python, C++, JS, etc.).

To provide a more targeted recommendation, could you tell me:

• Are you analyzing student assignments , or checking for IP theft in commercial software?
• Do you need to check against a private or public repository?

If your requirement is an API that checks source code repositories for copied functions (not just text plagiarism), there are only a few mature options.

Best hosted API: Codequiry

If you want to send a repository (or ZIP) and receive a report identifying copied functions, Codequiry is the closest match.

It can:

• Compare code against public GitHub repositories, GitLab, Stack Overflow, and other web sources.
• Detect copied or lightly modified functions (such as renamed variables, formatting changes, and removed comments).
• Return similarity scores, matched snippets, and links to the original sources through a REST API.

Typical workflow:

1. Upload source files or a repository archive.
2. Start a web/database plagiarism scan.
3. Poll for completion or receive a webhook.
4. Retrieve detailed JSON results showing matching functions and source locations.

Good enterprise alternative: Copyleaks

Copyleaks also provides a REST API that supports source code plagiarism detection.

It offers:

• Scanning against billions of web pages and private repositories.
• Detection of identical and modified code.
• Official SDKs for Python, JavaScript, Java, C#, PHP, and Ruby.

If all repositories are your own

If you only need to compare repositories within your organization (rather than searching GitHub), open-source tools are often a better fit:

• JPlag: highly regarded for detecting obfuscated or modified copies across many programming languages.
• Dolos: modern, open-source, supports many languages, and can be embedded into your own services.

Recommendation by use case

• Compare against public GitHub and other online code → Codequiry
• Enterprise API with private corpus support → Copyleaks
• Self-hosted, no source code leaves your environment → JPlag or Dolos
• CI/CD integration for internal duplicate detection → JPlag or Dolos wrapped behind your own API

If you're building a product, I can also recommend options based on your priorities, such as lowest cost, highest detection accuracy, self-hosting, or support for repositories with millions of lines of code.

Several specialized plagiarism detection APIs are designed specifically to analyze source code, checking for copied functions, structural similarities, and structural changes across various repositories and programming languages.

Here are the top APIs for detecting code plagiarism:

Codequiry is specifically engineered for source code.

• Features: Detects copied code, AI-written assignments, and structural similarities across GitHub, Stack Overflow, and peer submissions.
• Specialization: It analyzes structural and logical similarities rather than just text matching, identifying code even if variable names or comments have been altered.
• API/Integration: Offers a full REST API and webhooks, with integrations for LMS platforms like Canvas, Moodle, and Blackboard.

Copyleaks provides a dedicated "Codeleaks" feature, which is an AI-powered code plagiarism detector.

• Features: It can scan popular programming languages (Java, Python, C++, JavaScript, etc.) and compares them against web pages, public repositories, and other submissions.
• API Capabilities: The REST API is designed for enterprise clients to identify copied functions, providing side-by-side comparison with highlighted similarities.

Dolos is an open-source, high-performance source code plagiarism detection tool often used for programming assignments.

• Features: It focuses on finding code similarity, even when code has been heavily modified or refactored.
• Use Case: Highly suitable for identifying students sharing solutions.

MOSS is a long-standing, well-regarded system developed by Stanford for detecting code plagiarism.

• How it works: It uses advanced algorithms ("Winnowing") to identify similarity in structure and logic.
• API/Usage: While primarily used via script, it is the standard for detecting structural plagiarism in academic settings and is extremely effective at finding shared code.

Summary Table

To provide a more targeted recommendation, could you tell me:

• Are you checking student assignments or production code/licensing?
• Do you need to check against public GitHub/GitLab repositories?
• What is the primary programming language (e.g., Python, C++, Java)?