> What does that achieve?

Because then a user who wants to see the HDR image in all its full glory can do so. If the base image is not HDR, then there is nothing they can do about it.

> And why should "don't physically hurt my eyes" be an opt-in setting anyway instead of just the default?

While I very much support more HDR in the online world, I fully agree with you here.

However, I suspect the reason will boil down to what it usually does: almost no users change the default settings ever. And so, any default which goes the other way will invariably lead to a ton of support cases of "why doesn't this work".

However, web browsers are dark-mode aware, they could be HDR aware and do what you prefer based on that.

If you want to avoid eye pain then you want caps on how much brightness can be in what percent of the image, not to throw the baby out with the bathwater and disable it entirely.

And if you're speaking from iphone experience, my understanding is the main problem there isn't extra bright things in the image, it's the renderer ignoring your brightness settings when HDR shows up, which is obviously stupid and not a problem with HDR in general.

How about a user stylesheet that uses https://www.w3.org/TR/css-color-hdr-1/#the-dynamic-range-lim... ?