Because I checked out from paying attention to HTML's evolution years ago, it took me until very recently to hear about the new <details> element from HTML5. Put simply and bluntly, it's the first new HTML element I've heard of that actually sounds interesting to me. The reason for this is straightforward; it solves a problem that previously might have taken Javascript or at least complex CSS, namely the general issue of having some optional information on a web page that you can reveal or hide.

(That's the surface reason. The deeper reason is that it's the only new HTML5 tag that I've heard of that has actual browser UI behavior associated with it, instead of just semantic meaning.)

Now that I've heard of it, I've started to notice people using it (and I've also started to assume that if I click on the browser UI associated with it, something will actually happen; unfortunately Firefox's current rendering doesn't make it obvious). And when I look around, there are all sorts of things that I might use <details> for, both here on Wandering Thoughts and elsewhere, because optional or additional information is everywhere if you look for it.

(Here on Wandering Thoughts, one form of 'optional' information is comments on blog entries. Currently these live behind a link that you have to click and that loads a separate page, but <details> would let them be inline in the page and revealed more readily. Of course there are various sorts of tradeoffs on that.)

I was all set to make this a very enthusiastic entry, but then I actually looked at the the browser compatibility matrix from MDN and discovered that there is a little problem; <details> is not currently supported in Microsoft Edge (or IE). Edge may not be as popular as it used to be, but I'm not interested in cutting off its users from any of my content (and we can't do that at work). This can be fixed with a Javascript polyfill, but that would require adding Javascript and I'm not that interested.

Given that Edge doesn't support it yet and that IE is out there, it will probably be years before I can assume that <details> just works. Since the 'just works' bit is what makes it attractive to me, I sadly don't think I'm going to be using it any time soon. Oh well.

(HTML5 has also added a number of important input types; I consider these separate from new elements, partly because I had already somewhat heard about them.)