Here's the MDN page some of the sibling comments might want to see: https://developer.mozilla.org/en-US/docs/Web/HTML/Element/de...

The “new” thing (if you didn’t know it before) is that GitHub applies a collapse/expand behavior to <details> elements.

This is an actual HTML tag, not a github thing

https://jsbin.com/timafew/edit?html,output

Isn't that the default behavior of <details> in html documents? Am I missing something?

^ this is what I mean, yeah. Isn't that the expected behavior?

Your comment is accurate but I think its the fact that GitHub styles it in that way. I do wish it was possible to use markdown-types of elements in this way so that it could fallback on non-GitHub rendered web pages, or still look good in a text editor vs. HTML tags all over the place.

Maybe something like

^ Header

^^^

Collapsed

^^^

Similar to code blocks with the ``` syntax. I dunno.

> its the fact that GitHub styles it in that way

GitHub hardly styles it at all. It applies a margin-top on top of what normalize.css does. It's 99% your browser's default style sheet at work.

First we couldn't tell the difference between git and github. Now we can't tell the difference between browsers and github.