Don't use it, it totally blows. For another oddity to not use, check out the multiple select: https://developer.mozilla.org/en-US/docs/Web/HTML/Reference/...

Expecting users to press modifiers when clicking on these is so funny.

> Expecting users to press modifiers when clicking on these is so funny.

I mean… 5 year olds can figure out shift-click in Minecraft.

Trying to figure things out in a game is fun! Trying to figure things out on a website is a sign the UI sucks.

Learn it in a game, then use it on a website. It's a UI convention, not merely a quirk to a multi-select list.

Modifier keys are used elsewhere optionally on operating systems. But no other form control demands knowledge of modifier clicks. It's simply a useless bit of UI and should not be used.

> I don't see how this can be a replacement for javascript/XHR based autocomplete.

It can't do complex autocomplete. It's ok for simple cases only. I use it with a 25k long list to ease the input. Works well enough for this.

> If we can hand-off any JS functionality to native HTML or CSS, then users can download less stuff, and the remaining JS can pay attention to more important tasks that HTML and CSS can't handle (yet).

You can't. It's only supposed to be used for a limited list.

And even if you allow XHR and add options to a <datalist>, it still has terrible UX.