As I'm sure you all know, Chrome has a feature to highlight text using a
'text fragment directive', like this
<https://example.com/#:%7E:text=Domain>
I increasing see these, and I always thought that Firefox ignored them.

The other day I came upon this post on the Mudcat music site:
<https://mudcat.org/thread.cfm?threadid=172987#4194599>
with a link to Mudcat post SONGS ABOUT THE CONCERTINA

The poster intended the link to go to anchor songsabouttheconcertina,
which exists. But it doesn't (in Firefox/Android). The presence of the
:~:... part stops Firefox scrolling to the anchor.

(And in Chrome/Android it doesn't highlight the text either, though it
does scroll to the anchor. But if you remove everything after 'Songs' it
scrolls to the highlight and ignores the anchor.)

While investigating this curiosity I found this
<https://bugzilla.mozilla.org/show_bug.cgi?id=1779688>
then
<https://wicg.github.io/scroll-to-text-fragment/>

So it seems Firefox will support these text fragments.

But it's not clear to me whether a link like the the concertina one, which
both scrolls to an anchor and/or highlights text is valid. Section 3.3 of
that wicg link says it's not, but there is such a URL in example 8.

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Dave Royal wrote:

> it seems Firefox will support these text fragments.

Seems like a useful idea, when I link to a site (e.g.
legislation.gov.uk) I can be reasonably sure any section within a page
will have an element with an 'id=xxx' attribute that I can use.
Unfortunately most pages don't sprinkle potentially useful id attributes
throughout the content.

MDN documents them

<https://developer.mozilla.org/en-US/docs/Web/Text_fragments#syntax>

But <https://caniuse.com/?search=text%20fragment> just says they're
unofficial and firefox doesn't support it ...

On 6 Jan 2024 13:20:04 -0000 (UTC) Dave Royal wrote:
>[snip]
>So it seems Firefox will support these text fragments.
>
>But it's not clear to me whether a link like the the concertina one, which
>both scrolls to an anchor and/or highlights text is valid. Section 3.3 of
>that wicg link says it's not, but there is such a URL in example 8.

Having read a lot more of that wicg report I have concluded that having
_both_ a fragment-id and a text fragment directive _is_ valid. The
proposal is that the browser should highlight and scroll to the text
fragment, and scroll to the fragment-id as default - ie. it can't find the
text. (There are other options - eg. highlight _all_ cases of the text and
scroll to the first.)

So the 'correct' behaviour of that concertina link is to highlight and
scroll to 'Subject RE: Any December Songs?<newline>Fr' ('Fr' being the
start of the word 'From'). Chrome doesn't find that (because the 'Fr' is
part of an anchor element I think) and scrolls to the default fragment-id.

The choice of which to scroll to is not mandatory, so Firefox may do it
differently.

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