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Finding public code that matches GitHub Copilot suggestions

If you allow GitHub Copilot to make suggestions that match publicly available code, you can see references to the matching code on GitHub.com.

Note: GitHub Copilot code referencing is in public beta and is subject to change.

About code referencing in GitHub Copilot

You can opt to allow GitHub Copilot to suggest code completions that match publicly available code on GitHub.com. For more information, see "Managing Copilot policies as an individual subscriber."

If you have allowed suggestions that match public code, GitHub Copilot can provide you with details about the matching code when you accept such suggestions. This feature is called code referencing. It is currently only available in Visual Studio Code.

When you accept a code completion suggestion that matches code in a public GitHub repository, an entry is added to a GitHub Copilot log. The log entry includes a link to a page on GitHub.com where you can view references to similar code in public GitHub repositories.

The linked web page includes details of any license identified for the repository where the matching code was found. Having reviewed the references, you can decide how to proceed. For example, you can decide what attribution to use, or whether you want to remove this code from your project.

Notes:

  • Code referencing does not currently apply to code completion suggestions that you add to your code using GitHub Copilot Chat.
  • Code referencing currently only looks for matches of accepted Copilot suggestions. Matches to code you have written, or Copilot suggestions you have altered, is not checked for matches to public code.
  • Typically, matches to public code occur in less than one percent of Copilot suggestions, so you should not expect to see code references for many of the suggestions you accept.

How code referencing finds matching code

Copilot code referencing searches for matches by taking the code suggestion, plus some surrounding code, and comparing it against an index of all public repositories on GitHub.com. Code in private GitHub repositories, or code outside of GitHub, is not included in the search process. The search index is refreshed every few months. As a result, newly committed code, and code from public repositories deleted before the index was created, may not be included in the search. For the same reason, the search may return matches to code that has been deleted or moved since the index was created.

Using code referencing in Visual Studio Code

To use code referencing you must have allowed suggestions matching public code. For more information, see "Managing Copilot policies as an individual subscriber."

You can access code references from one of the GitHub Copilot logs in Visual Studio Code.

  1. In Visual Studio Code, open the Output window by selecting View > Output from the menu bar.

  2. In the dropdown menu at the right of the Output window, select GitHub Copilot Log.

    Screenshot of the Output window with "GitHub Copilot Log" selected from the dropdown menu.

  3. Leave the GitHub Copilot Log view displayed while you use GitHub Copilot in Visual Studio Code.

    When you accept a code completion suggestion that matches code in a public GitHub repository, an entry is added to the log.

    The log entry includes the following details:

    • The date and time you accepted the suggestion.
    • The name of the file in which the suggestion was added.
    • A message telling you that similar code was found, with the number and type of licenses.
    • A link to a page on GitHub.com.
    • The location in the file where the suggestion was added.
    • A snippet of part of the code that was suggested and added.

    Screenshot of the Output window showing a code referencing log entry.

    Note: The GitHub Copilot log is flushed when you close the editor.

  4. In the log entry, Ctrl+click (Windows/Linux) or Command+click (Mac) the link to view the code references on GitHub.com.

    The page lists the matches that were found, showing an excerpt from the relevant file. You can click on the file name to view the whole file.

    Screenshot of code references listed on GitHub.com.

    Matches may be found in multiple repositories with different, sometimes conflicting, licenses. You can use the checkboxes on the left of the page to show only the matches associated with a particular license.

    You should review all license information within a repository to verify that it applies to the matching code, as repositories may contain multiple licenses and these licenses are subject to human and non-human error.

    Note: The web page displaying the full set of details will remain available for three months.

Verifying the code referencing functionality

You can verify that code referencing is working by prompting Copilot to add some commonly used code and checking the output in the Copilot log.

  1. In Visual Studio Code, create a file called fizz-buzz.js.

  2. Open the Output window by selecting View > Output from the menu bar.

  3. In the dropdown menu at the right of the Output window, select GitHub Copilot Log.

  4. In the editor, type:

    function fizzBuzz()
    

    GitHub Copilot should suggest code to complete the function.

  5. Accept the suggestion by pressing Tab.

    If code referencing finds a match to public code, a log entry is added to the GitHub Copilot Log view.