From the paper...

Why "experimental" HTML?

Did you know that 90% of submissions to arXiv are in TeX format, mostly LaTeX? That poses a unique accessibility challenge: to accurately convert from TeX—a very extensible language used in myriad unique ways by authors—to HTML, a language that is much more accessible to screen readers and text-to-speech software, screen magnifiers, and mobile devices. In addition to the technical challenges, the conversion must be both rapid and automated in order to maintain arXiv’s core service of free and fast dissemination.

It's kind of fun to compare this formulation with the seemingly contradictory official arXiv argument for submitting the TeX source [1]:

> 1. TeX has many advantages that make it ideal as a format for the archives: It is plain text, it is compact, it is freely available for all platforms, it produces extremely high-quality output, and it retains contextual information.

> 2. It is thus more likely to be a good source from which to generate newer formats, e.g., HTML, MathML, various ePub formats, etc. [...]

Not that I disagree with the effort and it surely is a unique challenge to, at scale, convert the Turing complete macro language TeX to something other than PDF. And, at the same time, the task would be monumentally more difficult if only the generated PDFs were available. So both are right at the same time.

[1] https://info.arxiv.org/help/faq/whytex.html#contextual

No I mean _arXiv_ has had experimental support for generating HTML versions of papers for years now. If you visit arXiv, you'll see a lot of papers have generated HTML alongside the usual PDF, so I'm trying to understand whether the article discussed any new developments. It seems like it's not new at all

There are pretty often problems with figure size and with sections being too narrow or wide (for comfortable reading). The PDF versions are more consistently well-laid-out.