Compared to PDF format, HTML format is much more accessible because of browsers. Basically I can reuse my browser extensions to do anything I like without hassle, like translation, note taking, sending texts to LLMs, and so on.
For now, arXiv offers two HTML services: the default one in https://arxiv.org/html/xxxx.xxxxx , and the alternative one in https://ar5iv.labs.arxiv.org/html/xxxx.xxxxx , here 'x' is a placeholder for a number or digit.
The most glaring problem of the default HTML service is the coverage of papers. Sometimes it just doesn't work, e.g., https://arxiv.org/html/2505.06708 . The solution may be switch to alternative HTML service, e.g., https://ar5iv.labs.arxiv.org/html/2505.06708 .
Note that alternative HTML service also has coverage problem. Sometimes both HTML services fail, e.g. https://arxiv.org/abs/2511.22625 .