Occasionally, Domino Support may ask you to confirm the version of your domino deployment, or you may be looking at a version specific Knowledge Base article and are uncertain if it applies to you, or maybe you're just curious.
At the moment is no version information in the Domino UI. To find the version, use the URI format below.
That endpoint will return something similar to
The Domino version in the above example is "version":"4.4.2".
There is an existing feature request to add the version number to the UI to make this more straightforward, so at some point we should be able to note that this method is only valid for certain versions, but at the moment it is true for all Domino versions at least through 5.2.