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---
title: Boolean attribute (HTML)
slug: Glossary/Boolean/HTML
page-type: glossary-definition
spec-urls: https://html.spec.whatwg.org/#boolean-attributes
---
{{GlossarySidebar}}
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 not be present in the element tag. 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
- [Enumerated](/en-US/docs/Glossary/Enumerated)