What is the difference between readonly=“true” & readonly=“readonly”?

Question

What is the difference between:

and:

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Answer 1

readonly="readonly" is xhtml syntax. In xhtml boolean attributes are written this way. In xhtml 'attribute minimization' () isn't allowed, so this is the valid way to include boolean attributes in xhtml. See this page for more.information.

If your document type is xhtml transitional or strict and you want to validate it, use readonly="readonly otherwise readonly is sufficient.