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---
tags:
- html
- web
---
`content` attribute required
Pragma directive: `http-equiv` attribute (its value is pragma directive)
Named: `name` attribute.
# Pragma directive
[7 defined](https://html.spec.whatwg.org/multipage/semantics.html#pragma-directives)
most useful:
`<meta http-equiv="content-security-policy" content="default-src https:" />`
[content values](https://developer.mozilla.org/docs/Web/HTTP/Headers/Content-Security-Policy)
Specify allowed server origins and script endpoints, protecting against cross site scripting attacks.
# Named
- keywords; obsolete due to snake-oil salespeople
- description; useful for SEO
- robots
- `content="noindex, nofollow"`
- `content="index, follow"`
### OpenGraph
[Protocol](https://ogp.me/)
Control how social media sites display links.
Have a `property` attr instead of `name`.
Facebook media card:
```
<meta property="og:title" content="Machine Learning Workshop" />
<meta property="og:description" content="School for Machines Who Can't Learn Good and Want to Do Other Stuff Good Too" />
<meta property="og:image" content="http://www.machinelearningworkshop.com/image/all.png" />
<meta property="og:image:alt" content="Black and white line drawing of refrigerator, french door refrigerator, range, washer, fan, microwave, vaccuum, space heater and air conditioner" />
```
Twitter uses something else: [Twitter card markup](https://developer.twitter.com/en/docs/twitter-for-websites/cards/overview/markup)
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