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The 30 Boolean Attributes of HTML

Published on May 19, 2020 (updated Oct 22, 2026), filed under , . (Share this post, e.g., on Mastodon.)

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There are Boolean attributes in HTML and, unless I err somewhere, there are [now more than] two dozen of them. Here’s a quick rundown of what makes for a Boolean attribute, and what Boolean attributes there are in current HTML.

What is a Boolean at all? Citing the The Web Development Glossary, a Boolean is “a data type that has one of two possible values (usually denoted true and false).”

What is a Boolean attribute? A Boolean attribute is an attribute that can only be true or false.

How does a Boolean attribute work? According to the HTML specification:

The presence of a boolean attribute on an element represents the “true” value, and the absence of the attribute represents the “false” value.

Yet note:

The values “true” and “false” are not allowed on boolean attributes. To represent a false value, the attribute has to be omitted altogether.

So, what Boolean attributes are there?

The Boolean Attributes

  1. allowfullscreen
  2. alpha
  3. async
  4. autofocus
  5. autoplay
  6. checked
  7. controls
  8. default
  9. defer
  10. disabled
  11. formnovalidate
  12. headingreset
  13. inert
  14. ismap
  15. itemscope
  16. loop
  17. multiple
  18. muted
  19. nomodule
  20. novalidate
  21. open
  22. playsinline
  23. readonly
  24. required
  25. reversed
  26. selected
  27. shadowrootclonable
  28. shadowrootcustomelementregistry
  29. shadowrootdelegatesfocus
  30. shadowrootserializable

Yes. That’s it.

Update (October 21, 2022)

The list now strictly follows the HTML specification’s attributes overview. That means it doesn’t contain Boolean attributes found on legacy and obsolete elements anymore, like truespeed.

About Me

Portrait sketch of Jens Oliver Meiert.

I’m Jens (long: Jens Oliver Meiert), and I’m an engineering lead, guerrilla philosopher, and indie publisher. I’ve worked as a technical lead and manager at various companies (e.g., Google); I’m an active web and tool developer (code optimization, digital defense), a contributor to web standards (like HTML, CSS, WCAG), and a book author (O’Reilly, Frontend Dogma). Stay in touch.