How can I know that, My add-on user are use new or old JIRA UI in cloud

[Piyush Patel]

Is there any api or something that give me hint whether user is use new UI or old UI.

[Nic Brough -Adaptavist- · Accepted solution]

Look at the distribution of Jira.  If you are on Server, it's the old UI.  If it's Cloud, it's the new one. Mind you, you can't write an add-on that works on both, so you don't need to think at all - the Cloud version of your add-on will be using new, the Server version, old.

If you're talking about the new look and feel (Jira 7.6ish, Confluence 6.7ish), then no, but you can just look at the version of Jira and Confluence.