Characters allowed in middle of HTML tag name

Characters that are may be part of HTML tag names. These are less strict that the first character

Created Jan 30, 2026

Updated Jan 30, 2026

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CategoryHTML Parsing

VisibilityPublic

TypeXSS

CharsetUTF-8

Template used:

<a$[chr] id="test">

Code used after fuzz:

document.getElementById('test').tagName.length > 1 && log(i)

Sample payloads

<a0x0B id="test">