XML 1.1 doesn’t support all of ASCII either. https://www.w3.org/TR/xml11/#NT-Char https://www.w3.org/TR/xml11/#NT-Char: > Char ::= [#x1-#xD7FF] | [#xE000

XML 1.1 doesn’t support all of ASCII either. https://www.w3.org/TR/xml11/#NT-Char https://www.w3.org/TR/xml11/#NT-Char: > Char ::= [#x1-#xD7FF] | [#xE000-#xFFFD] | [#x10000-#x10FFFF] /* any Unicode character, excluding the surrogate blocks, FFFE, and FFFF. */ I’m puzzled at the total non-mention of U+0000 in the document, which is a valid Unicode and ASCII character but is not supported by this definition of Char. So it seems like it’s actually (and using better terminology) “any Unicode scalar value, except U+0000, U+FFFE and U+FFFF”. The same restriction you noted on entity encoding still holds: https://www.w3.org/TR/xml11/#NT-CharRef https://www.w3.org/TR/xml11/#NT-CharRef