I noticed that when I browse through stuff in the forum, the URL changes but the browser window doesn’t visibly refresh. I think it’s really cool, how does this work?
Maybe this:
Using the HTML5 History API | CSS-Tricks - CSS-Tricks
This lead to the old hashbang method of changing the URL without a full page refresh. Famously, Twitter used to do things this way and was largely criticized for it (a hash not being a “real” resource location).
I took a quick look through the page source and it seems like they’ve built the forum using EmberJS. If I’m not mistaken this is a SPA framework (single-page application), which uses a router to display different sections without refreshing the entire page.
Robin Ward “eviltrout” wrote about this technique:
https://eviltrout.com/2013/02/16/infinite-scrolling-that-works.html
It has been improved a lot further since that post, but the fundamentals are still the same. And like @nameToReachPeople correctly pointed out, it’s done by using the History API.