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Elchi3 merged 5 commits into from
Jul 17, 2025
Merged

HTML enumerated attributes are case-insensitive #40377

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HTML enumerated attributes are case-insensitive
Elchi3 Jul 15, 2025
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Add a sentence about IDL reflection
Elchi3 Jul 15, 2025
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Document enumerated reflected attributes in DOM guide
Elchi3 Jul 16, 2025
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Elchi3 Jul 16, 2025
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Update files/en-us/glossary/enumerated/index.md
Elchi3 Jul 17, 2025
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2 changes: 1 addition & 1 deletion files/en-us/glossary/enumerated/index.md
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Expand Up @@ -9,7 +9,7 @@ In computer science, an **enumerated** type is a data type consisting of a limit

## HTML enumerated attributes

In HTML, [enumerated attributes](https://html.spec.whatwg.org/multipage/common-microsyntaxes.html#enumerated-attribute) are attributes with a limited, predefined set of text values. For example, the global HTML [`dir`](/en-US/docs/Web/HTML/Reference/Global_attributes/dir) attribute has three valid values: `ltr`, `rtl`, and `auto`.
In HTML, [enumerated attributes](https://html.spec.whatwg.org/multipage/common-microsyntaxes.html#enumerated-attribute) are attributes with a limited, predefined set of text values. For example, the global HTML [`dir`](/en-US/docs/Web/HTML/Reference/Global_attributes/dir) attribute has three valid values: `ltr`, `rtl`, and `auto`. Like for HTML tag names, HTML enumerated attributes and their values are case-insensitive, so `LTR`, `RTL`, and `AUTO` will also work. The IDL-reflected property, {{domxref("HTMLElement.dir")}}, always returns a canonical value as provided in the specification (lowercased values in this example).

Each enumerated attribute has a default value for when the attribute is present without a value (the value is missing), and a default value for when the attribute is assigned an invalid value. Unlike {{Glossary("Boolean/HTML", "Boolean attribute")}} HTML attributes — which are always true when the attribute is present whether the value is present, omitted, or invalid — with enumerated HTML attributes, the default for an omitted value may be different from the default for invalid values. For example, the global HTML [`contenteditable`](/en-US/docs/Web/HTML/Reference/Global_attributes/contenteditable) attribute has two valid keywords: `true` and `false`. If the attribute is present but no value is set, the value is `true`. If a value is set, but is invalid, such as `contenteditable="contenteditable"`, the value maps to a third state, `inherit`.

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