Wikipedia got a new layout last week. It mostly looks the same to me, except the new sidebar with a document outline takes up more horizontal space than the old sidebar. I'm not a fan of wasting space, and neither are some other people I've heard from. Fortunately, my web browser extension StopTheMadness has a solution, as usual. You can use the custom redirects feature of StopTheMadness to get back the old Wikipedia layout. This feature is available on both macOS and iOS.
URL matching pattern: /^https://en\.wikipedia\.org/[^?]+$/
Replacement: $&?useskin=vector
Copy and paste from above to ensure it's right. The pattern is a regular expression. You don't need to understand the technical details, but essentially it looks for a Wikipedia URL without a query string and then adds the query ?useskin=vector to the end.
If you use a non-English version of Wikipedia, just replace "en" with your language prefix, such as "de" for the German version.
Here's an example of the new Wikipedia layout with sidebar outline.
And here's the old layout after StopTheMadness redirect. Notice that the same content takes less vertical space.
StopTheMadness is available in the iOS App Store and Mac App Store.