Why did YouTube put a type= attribute in iframe for embedded video?

Question

When going to YouTube, it gives a embed code such as

<iframe title="YouTube video player"
class="youtube-player" type="text/html" width="640" height="385"
src="http://www.youtube.com/embed/QRvVzaQ6i8A?rel=0">
</iframe>

Note that the

type="text/html"

is not valid html. There's no such attribute for iframe tag.

could anyone explain why google put that? I guess it's for some practical reason, but i couldn't guess what.

PS you can get the embed code by going here http://www.youtube.com/watch?v=QRvVzaQ6i8A

Answer 1

It's not a mistake, it's the embed code for the HTML5 Youtube Player.

When it comes to validating HTML, you have to remember that HTML5 allows the content author to use non-standard elements and attributes and the document should still work. Additionally, non-standard markup that becomes popular enough can be documented and become an extension to the HTML5 spec.

Answer 2

I guess it is a mistake from Google itself. I suspect a mistake. It was not part of HTML4, and it is not part of HTML5. You can safely ignore it and remove it.

on the type attribute topic: The type on the object element is conforming but obsolete. It has never been really used by browsers to guess the content of the URI served.