twittercard

MetaExtension twitter:card

Is used to specify the type of twitter card you want to use for your website if someone tweets about it.

Read more about twitter:card on Twitters Developer Platform.

Usage

<meta name="twitter:card" content="summary">

content may be:

You can define only one twitter:card per site.

W3

In the WHATWG Wiki

Up to date: v2.3.3