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HTML Checking for Large Sites

Rocket Validator integrates the W3C Validator HTML checker into an automated web crawler.

The allowfullscreen attribute is used to allow an iframe to activate fullscreen mode. As a boolean attribute, it should only be declared without any value.

Here is an example of correct usage:

<iframe src="" allowfullscreen></iframe>

However, this is now a legacy attribute, and has been redefined as allow="fullscreen", as part of the more general Permissions Policy:

<iframe src="" allow="fullscreen"></iframe>

Learn more:

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