Or how to match an Atlassian product and version to a compatible AUI Sandbox.

AUI Sandbox (latest) is really useful when fitting design patterns to Atlassian add-ons.

I keep hitting problems though. Paste some example markup into (say) a Confluence add-on using the latest version of Confluence and the UI doesn't always look the same.

Why's that? Well. The latest released version of Confluence doesn't use the latest version of AUI. That's expected I suppose, but damn, I want the correct version. How?

In the web console in your Atlassian product type AJS.version then take a look here – https://docs.atlassian.com/aui/ – for the closest fit. You'll be able to browse down the directory structure to a compatible AUI Sandbox.

Check out these retro versions of AUI Sandbox – 3.3.0, 3.6.0 & 4.0 – pretty wild, huh?