Jens Oliver Meiert

The 24 Boolean Attributes of HTML

Post from May 19, 2020 (↻ May 25, 2022), filed under .

There are Boolean attributes in HTML and, unless I err somewhere, there are 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. async
  3. autofocus
  4. autoplay
  5. checked
  6. controls
  7. default
  8. defer
  9. disabled
  10. formnovalidate
  11. ismap
  12. itemscope
  13. loop
  14. multiple
  15. muted
  16. nomodule
  17. novalidate
  18. open
  19. playsinline
  20. readonly
  21. required
  22. reversed
  23. selected
  24. truespeed

Yes. That’s it.

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About Me

Jens Oliver Meiert, on April 29, 2020.

I’m Jens Oliver Meiert, and I’m an engineering lead and author. I’ve worked as a technical lead for Google, I’m close to the W3C and the WHATWG, and I write and review books for O’Reilly. Other than that, I love trying things, sometimes including philosophy, art, and adventure. Here on meiert.com I share some of my views and experiences.

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Perhaps my most comprehensive book: The Web Development Glossary (2020). With explanations and definitions for literally thousands of terms from Web Development and related fields, building on Wikipedia as well as the MDN Web Docs. Available at Apple Books, Kobo, Google Play Books, and Leanpub.

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