About visibility for GitHub Apps
You can make your GitHub App public or private. If you set your GitHub App to public, any user on GitHub.com or GitHub Enterprise Cloud can install it. If you set your GitHub App to private, it can only be installed on the account that owns the app.
You can create a GitHub App from your individual user account and make it available for organization accounts to install. You do not need an enterprise plan or an organization account to create a GitHub App for organizations even if the organization is owned by an enterprise on GitHub Enterprise Cloud.
If you want to make your app available to GitHub Enterprise Server instances, then you need to use an app manifest. The GitHub Enterprise Server instance will create the app from the manifest and provide you with the required information. For more information, see "Creating a GitHub App from a manifest."
If it is important for GitHub Enterprise Server users to be able to use your tool, consider using GitHub Actions instead of a GitHub App. Public actions are available on GitHub Enterprise Server instances with GitHub Connect. For more information, see "Enabling automatic access to GitHub.com actions using GitHub Connect" and "About GitHub Actions for enterprises."
For information about changing the visibility of a GitHub App, see "Modifying a GitHub App."
Public installation flow
Public GitHub Apps have a landing page with an Install button, so that other people can install the app in their repositories. If your GitHub App is public to all users on GitHub.com, you can also choose to publish it to GitHub Marketplace. For more information, see "About GitHub Marketplace."
Private installation flow
Private GitHub Apps can only be installed on the user or organization account of the app owner. Limited information about the app will exist on a landing page for the app, but the Install button will only be available to organization owners and app managers for the organization that owns the app, or the personal account if the GitHub App is owned by an individual account.