@Lady It actually has a surprisingly small set of rdepends within Ubuntu. Some important packages, like Postgres, but mostly desktop software besides Postgres, Icecast, and Asterisk, and it's hard to say the latter have all too many users. There's Ruby's Nokogiri, but given the near-weekly security updates to that, I might almost prefer someone Rewrite it in Rust (or literally anything).
@aschmitz pretty sure all web browsers depend on either it directly or a fork of it (statically linked, probably, and i’m not sure how exactly the code is joined together)
if not, i’d be interested in finding out whatever they ARE using
@Lady WebKit uses libxslt, at least it did when I packaged it.
Firefox has its own custom HTML 5 parser, originally developed around 2009 and somewhat based off the HTML 5 standard parsing algorithm and a Java reference implementation, unimaginatively just called "parser". It does vendor a copy of Expat for pure XML.
See also:
https://johnresig.com/blog/html-5-parsing/
https://hacks.mozilla.org/2010/05/firefox-4-the-html5-parser-inline-svg-speed-and-more/
https://hg-edge.mozilla.org/mozilla-central/file/tip/parser