Qodana 2021.2 Help

About Qodana Clone Finder

official project

Qodana Clone Finder compares a queried project against a number of reference projects and lists all duplicate functions ranked by their importance. In future, search by classes and files will be added.

The tool is designed to prevent problems rather than face the consequences down the line. By supporting CI integration, Clone Finder makes clone detection a routine check and reports borrowed code before it can lead to trouble.


Clone Finder uses a block-based bag-of-tokens approach to clone detection that applies different similarity thresholds depending on the function size and token length, thus yielding diverse relevant results.

Clone types and importance score calculation

Clone Finder uses a logistic regression model to estimate the importance score of clones based on features like the number of identifiers, entropy of the identifiers, and average length of the identifiers, finding the following types of clones:

  • Identical code fragments with possible variations in whitespaces, layout, and comments

  • Syntactically equivalent fragments with some variations in identifiers, literals, types, whitespaces, layout and comments

  • Syntactically similar code with inserted, deleted, or updated statements.

You can see a sample report in Clone Finder Output.

Types of problems prevented

  • Penalties for the unlicensed use of third-party code

  • Excessive project maintenance costs due to overgrown codebases

  • Increased security risks because fixing detected vulnerabilities across all instances of the copied code can be difficult

Try it now

Analyse a project locally

To start, pull the image from Docker Hub (only necessary to get the latest version):

docker pull jetbrains/qodana-clone-finder

and run the analysis locally:

docker run --rm -it -p 8080:8080 \ -v <queried-project-directory>/:/data/project/ \ -v <reference-projects-directory>/:/data/versus/ \ -v <output-directory>/:/data/results/ \ jetbrains/qodana-clone-finder --show-report

where <queried-project-directory>, <reference-projects-directory>, and <output-directory> are full local paths to the directories that contain, respectively, the project source code, one or more projects to compare against, and the analysis results.

Check the results in your browser at http://localhost:8080.

Read our Docker guide for more options and details related to the Clone Finder execution.

Run at GitHub

You can set up a workflow in your GitHub repository using the GitHub action we published.

Supported languages

PHP, Java, and Kotlin are already supported. Eventually, all languages and technologies covered by JetBrains IDEs will be added.


By using Qodana linters, you agree to the JetBrains EAP user agreement and JetBrains privacy policy.

Last modified: 03 June 2021