Processing non-ascii tags and attributes in HTMLParser
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@serhiy-storchaka is already working on this.
Since Nov 19, 2025.
3.13
3.14
3.15
stdlib
type-bug
- Dominant language
- Python
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Description
Bug report
html.parser.HTMLParser convert names of tags and attributes to lower case. But the HTML5 specification only prescripts converting ASCII upper alpha characters to lower case.
- https://html.spec.whatwg.org/multipage/parsing.html#tag-name-state
- https://html.spec.whatwg.org/multipage/parsing.html#attribute-name-state
There are some non-ASCII characters which are converted to ASCII lowercase characters (e.g. "ß" -> "ss", "K" (U+212A) -> "k", "ſ" -> "s"). They will be parsed differently by HTMLParser and any other parser or browser.
Linked PRs
- gh-141758
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