The OOjs UI library has a useful demos directory, which shows off each of the widgets available. Similarly, VisualEditor also has a demos directory, and I imagine other projects do (or would if it became an established pattern.
It would be really great if we could somehow expose these alongside their projects' documentation, so we can point people to a living thing rather than telling them to checkout the repo and play. Something like…
https://doc.wikimedia.org/VisualEditor/master/
https://doc.wikimedia.org/VisualEditor/master/demos/
https://doc.wikimedia.org/VisualEditor/0.1.0/
https://doc.wikimedia.org/VisualEditor/0.1.0/demos/
https://doc.wikimedia.org/OOjs-UI/master/
https://doc.wikimedia.org/OOjs-UI/master/demos/
https://doc.wikimedia.org/OOjs-UI/1.0.6/
https://doc.wikimedia.org/OOjs-UI/1.0.6/demos/
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**Version**: unspecified
**Severity**: enhancement