Jeremy Keith wrote a (typically great) post about metacrap, the unneccesarily verbose and repetitive metadata in the head of web documents, that’s required for content to be more easily shareable across social media. I fully agree with his broad point — there’s an awful lot of crap in head — but there’s a flaw in his initial examples. It’s explained in this extract from Twitter’s Getting Started [with Cards] Guide:

You’ll notice that Twitter card tags look similar to Open Graph tags, and that’s because they are based on the same conventions as the Open Graph protocol. If you’re already using Open Graph protocol to describe data on your page, it’s easy to generate a Twitter card without duplicating your tags and data.

So actually the metadata you need to cater for most social sharing is Open Graph, with a few extra tags just for Twitter:

<meta name="twitter:card" content="summary">
<meta name="twitter:site" content="@adactio">
<meta property="og:url" content="https://adactio.com/journal/9881">
<meta property="og:title" content="Metadata markup">
<meta property="og:description" content="So many standards to choose from.">
<meta property="og:image" content="https://adactio.com/icon.png">

I mean, it’s still perhaps too much, and (as pointed out) would probably be best written as JSON-LD in the manifest. But there’s no redundancy, so is not quite as bad as painted in Jeremy’s article, even with his elegant squishing solution.