allowfullscreen is a boolean property of the
If you embed a <iframe></iframe>
into a web page and want it to be displayed in full screen (such as playing videos), the allowfullscreen
attribute is very critical. Its function is simple: allows this iframe to enter full screen mode when the user clicks the "Full Screen" button.

What is allowfullscreen
attribute?
allowfullscreen
is a new Boolean attribute added to the <iframe></iframe>
element in HTML5 to control whether the iframe is allowed to enter the full screen state.
As long as you add this attribute to the iframe tag, the browser will know: "Oh, this embedded content can be full screen."
For example:

<iframe src="video.html" allowfullscreen></iframe>
After writing this way, if the content in the iframe supports full-screen function (such as a video player), the user can click the full-screen button to enlarge the screen.
Why do I need to use allowfullscreen
?
By default, browsers may limit certain behaviors of iframes, including full-screen operations, for security and user experience reasons. So if you want the content in the iframe to be full screen, you must explicitly add the allowfullscreen
attribute.

Common scenarios include:
- Embed YouTube or Vimeo videos
- Display content that requires full screen experience, such as WebVR, games or presentations
- Provide picture-in-picture or other multimedia interaction functions
If you do not add this attribute, the user may click the "Full Screen" button but there is no response, which will cause confusion.
Notes on using allowfullscreen
Although it is simple to use, there are still several details to pay attention to:
- Don't spell the word wrong :
allowfullscreen
has no hyphen, spelling intoallow-fullscreen
or other forms is invalid. - No assignment is required : it is a Boolean property, as long as it exists, it means "allowed", and does not need to be written as
allowfullscreen="true"
. - Good compatibility : modern mainstream browsers (Chrome, Firefox, Edge, Safari) all support it.
- Use it in conjunction with other permissions : Sometimes you may also need to add
allow="fullscreen; autoplay"
to ensure that multiple functions take effect at the same time.
In addition, some platforms (such as some CMS or editors) may automatically add this property to you, but it may not be added. You need to check it yourself.
Can you not use allowfullscreen
?
Technically, you can not add it, but the result is: iframe cannot be full screen.
Unless you explicitly want to ban users from full screen operations (such as advertising or certain layout-sensitive content), it is recommended that you always add this attribute.
Of course, it is also possible to request full screen through JavaScript, but that's another topic, and it usually applies to the entire page or a certain DOM element, rather than an embedded iframe.
Basically that's it. Adding an allowfullscreen
to an iframe seems a trivial matter, but it is easy to ignore it in actual use, especially when you debug an embedded content that cannot be fully screen, remember to look back and see if you have forgotten this property.
The above is the detailed content of The HTML `iframe` `allowfullscreen` Attribute. For more information, please follow other related articles on the PHP Chinese website!

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