Boolean attribute (HTML)
A boolean attribute in HTML is an attribute that represents true
or false
values. If an HTML tag contains a boolean attribute - no matter the value of that attribute - the attribute is set to true
on that element. If an HTML tag does not contain the attribute, the attribute is set to false
.
If the attribute is present, it can have one of the following values:
- no value at all, e.g.
attribute
- the empty string, e.g.
attribute=""
- attribute's name itself, with no leading or trailing whitespace, e.g.
attribute="attribute"
Note: The strings "true" and "false" are invalid values. To set the attribute to false
, the attribute should be omitted altogether. Though modern browsers treat any string value as true
, you should not rely on that behavior.
Here's an example of a HTML boolean attribute checked
:
html
<!-- The following checkboxes will be checked on initial rendering -->
<input type="checkbox" checked />
<input type="checkbox" checked="" />
<input type="checkbox" checked="checked" />
<!-- The following checkbox will not be checked on initial rendering -->
<input type="checkbox" />
See also
- Boolean attributes
- Boolean attributes in HTML specification
- Related glossary terms: