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Home < Documentation < Nightly < Developers < Tutorials < BuildTestPackageDistributeExtensions

For the latest Slicer documentation, visit the read-the-docs.

To learn what is an extension, see here

Step-by-step: How to create, publish, distribute and maintain an extension ?

  • Scan through the user and developer extension FAQs
  • Inform a community about your plans on the Slicer forum to get information about potential parallel efforts (other developers may already work on a similar idea and you could join or build on each other's work), past efforts (related tools might have been available in earlier Slicer versions or in other software that you may reuse), and get early feedback from prospective users. You may also seek advice on the name of your extension and how to organize features into modules. All these can save you a lot of time in the long term.
  • Optional (required if developing loadable or CLI module types): Build Slicer application in Release. Not needed if you only develop Python modules.
  • Use the Extension Wizard module in Slicer to create an extension that will contain your module(s). Learn more about ExtensionWizard capabilities here. To learn about extension description file format see here
  • Upload source code of your extension to a publicly available repository. It is recommended to start the repository name with "Slicer" (to make Slicer extensions easier to identify) followed by your extension name (for example, "Sequences" extension is stored in "SlicerSequences" repository). However, this is not a mandatory requirement. If you have a compelling reason not to use Slicer prefix, please make a note while making the pull request.
    • GitHub is recommended (due to large user community, free public project hosting): join Github and setup Git
    • Extension Wizard command-line interface can upload source code of your extension to GitHub:
$ bin/slicerExtensionWizard --publish ~/Slicer-MyExtension/
  • Implement your extension. Hack, hack, hack :).
  • Create documentation page for your extension
  • Optional (only needed, if you want to upload test data to MIDAS or troubleshoot extension upload problems): Create an account on the extension server and obtain an API Key. You will then use your midas login and api key to substitute <YOUR-MIDAS-LOGIN> and <YOUR-MIDAS-APIKEY> in the examples. Go to NA-MIC community and click on Join community

  • Optional (required for loadable and CLI modules): Build your extension
  • Test your extension:
    • If you have built your extension then build the PACKAGE target to create a package file that you can install from the Extension Manager by clicking the small tool icon in the top-right corner.
    • If you have not built your extension then set up your extension manually: Build your extension
  • If you consider your extension is ready for distribution (see contribution checklist), contribute it to the ExtensionsIndex:
    • Fork ExtensionIndex repository on GitHub by clicking Fork button on page
    • Add your .s4ext file to your forked repository: it can be done using a git client or simply by clicking Upload files button
    • Create a pull request: by clicking Create pull request button
    • Note: the Extension Wizard can automate this by the following command:
$ bin/slicerExtensionWizard --contribute ~/Slicer-MyExtension/

Contribution Checklist

  • Wait for your pull request to be merged. Respond to comments posted on the pull request. The following checklist will automatically be associated with your pull request.

Continuous Integration

If you shared your extension by using the ExtensionWizard, make sure you know about the Slicer testing dashboard:


The dashboard will attempt to check out the source code of your extension, build, test and package it on Linux, MacOSX and Windows platforms.

To find your extension, use the following link replacing Slicer-MyExtension with the name of your extension:

For example, here is the link to check the status of the SlicerDMRI extension:

If you see red in any of the columns for your extension, click on the hyperlinked number of errors to see the details.

Always check the dashboard after you first introduce your extension, or after you make any changes to the code!