Order of picked up meta tags in the html-head

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2 weeks ago

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I was wondering if someone could explain how social media rich previews define which og:title to pick.

I use wordpress and for certain pages I insert php echo strings to inject them into the <head>. I choose to do that to change certain titles and descriptions into more commercial texts. What obvisouly happens is that there are 2 og:title meta tags; my injected one and the Wordpress backend page title.

Once I was told that the first meta tag in the top of the <head> will be picked as thé meta tag to be picked up for rich previews for example, but this seems not to happen (anymore).

Below is my current situation and exact order of meta tags in the <head>:

<html>
	<head>
		<meta charset="UTF-8">
		<title>EXAMPLE</title>
		<link rel="canonical" content="https://example.com">
		<meta name="description" content="description">
		<meta name="subject" content="example">
		<meta property="og:title" content="og:title #1"> // my injected og:title
		<meta property="og:description" content="description">
		<meta property="og:url" content="https://example.com">
		<meta name="twitter:title" content="EXAMPLE">
		<meta name="twitter:description" content="description">
		<link rel="alternate" href="https://example.com" hreflang="nl-nl">
		<link rel="alternate" href="https://example.com" hreflang="nl-be">
		<title>EXAMPLE</title>
		<meta property="og:title" content="og:title #2"> // the og:title being used
		<meta property="og:type" content="website">
		<meta property="og:url" content="https://example.com">
	</head>	
</html>

What happens is that Whatsapp and Facebook are taking the 2nd og:title meta tag, which doesn't make sense in my opinion.

Changing the title page in the backend is not a solution, because it becomes something like Check out our wonderful shop!, this is not user friendly. Also I'm not a fan of Yoast, because Yoast loads extra code into the pages, which I don't want.

Who knows a solution to this, or can explain why this is happening?


Update & Answer
Thanks to Chris I understand that og: meta tags are being scanned from top to bottom in the <head>, and updates the 2 identical properties with the last one that is being scanned. This RDFa process is typical for apps like Facebook, Whatsapp, Twitter. One exception: og:image seems to be needed in the top, it doesn't override a second or third one below it.

Google Search related tags are being picked up by the first one in the top of the <head> and keeps that one as "first come, first serve".

Solution: I will inject og: tags into the bottom of the <head> and the other ones will be kept in the top. Tested it and it works.

1 answers

1

Facebook and other apps generally use their own slimmed down versions of RDFa parsing, which from my understanding is a way to parse meta data from xml and html documents. From what I was reading, it seems that as the parser goes through your html page, it will add the first metadata piece it finds to it's "current subject", and if it finds another one with the same name, it will then overwrite the "current subject" with the updated info.

It seems like a pretty complicated topic, so I suppose the simple answer would just be that their parser will always take the last meta data tag and use that.

To fix the issue, I would see if you can inject your custom og:title/metadata below the one autoinjected by Wordpress.

You can read more about RDFa parsing here