Jira Service Management: Customize your portal URL
Can you use a custom URL for your Jira Service Management portal?
With Jira Service Management Server, you would have the option of configuring the Jira base URL of your instance. The URL's of your Jira Service Management portals will include elements of this base URL, but the full URL's of the portals themselves will be created by the application.
With Jira Service Management Cloud, the option for a custom domain is currently not an available feature you can configure for your Jira Service Management portal on your Atlassian Cloud site.
We have an accepted feature request, allow custom domains for Cloud apps, open in our public issue tracker that you can comment on, vote on, or watch for future updates from our Atlassian Cloud product team.
You can also explore additional options within our Atlassian Community with fellow Atlassian users on topics such as configuring a friendly URL for Jira Service Management.