This blink is in a specific UI XML dialect, not HTML.

True, it has never been in an HTML standard, however it was definitely a documented part of early HTML.

The blink element was in Netscape Navigator's HTML dialect in 1993/94, when early HTML was still just hitting IETF RFCs / DRAFTs, you can find blink in the Netscape HTML developer documentation from just after that era, DevEdge. It was never in NCSA Mosaic, the other big GUI browser of the era.

Later on in the process of being standardized, when it was more W3C than IETF albeit still mainly the same people, Netscape agreed to drop blink from the proposals if Microsoft dropped marquee, so in that sense yes, it was never in a standardized version of HTML, but many tags in active use at the time were never in a standards doc.

See here https://www.w3.org/People/Raggett/book4/ch02.html for some history from w3c, who went on to become the formal custodians of HTML after the IETF days.

Edit: here's the earliest Netscape Developer Docs I can see on archive.org https://web.archive.org/web/19961115043739/http://developer....

Blink shows that the webs often touted absolute backwards compatibility can be broken for really petty reasons.

At least these days you can easily bring back the fun:

  blink {
    animation: blink 1s steps(5, start) infinite;
  }
  @keyframes blink { to { visibility: hidden } }

Yeah that's where the concept of the blink tag originates, the now deprecated HTML tag. But what's covered in the blog post refers specifically to a hidden (and AFAIK undocumented) blink tag that exists in the Android XML layout view system, which is an independent thing from the system WebView browser (that I assume probably still contains some code for blink tags, but that wouldn't be a surprising discovery). I don't know if there are any other built-in tags in Android views that really map to HTML tags otherwise.

It actually seems like there’s another Easter egg if you google “blink tag”: https://www.google.com/search?q=blink+tag

(Doesn’t seem to trigger on iOS, but works in Chrome and Firefox on desktop)

Disappointing, the result HTML doesn't actually use <blink> tags.