Open Graph tags are lines of code in a page’s HTML head that tell social platforms and messaging apps what to show when someone shares the link: the title, description, image and address. Without them, Facebook, LinkedIn, WhatsApp, Slack and similar apps guess, often picking a logo, a cookie banner or the wrong text.
How Open Graph tags work
The Open Graph protocol was created by Facebook in 2010 and is now read by most platforms that build link previews. Each tag is a meta element with a property name and a content value. The core set is:
- og:title The headline for the preview, which can differ from the title tag used in search results.
- og:description A sentence or two shown under the title.
- og:image The full address of the image to display.
- og:url The canonical address of the page, so shares of different versions of the URL are grouped together.
- og:type Usually “website” or “article”.
- og:site_name and og:locale, the site’s name and language. For a UK site the locale is en_GB.
X, formerly Twitter, uses its own card tags, such as twitter:card set to summary_large_image, but falls back to Open Graph values for the title, description and image when its own are missing. Most platforms store the preview the first time a URL is shared, which is why a corrected image may not appear until that cache is refreshed.
For images, 1,200 by 630 pixels is a widely used size that displays well across the main platforms. Keep important text away from the edges, because some apps crop previews to a square.
Why it matters
Open Graph tags do not affect Google rankings directly. They affect what happens when your pages travel beyond search. A blog post shared on LinkedIn, a service page sent round a WhatsApp group, a product link posted on Facebook: each shows a preview, and an accurate, attractive one draws more clicks than a grey box with a cropped logo. A lot of sharing happens in private messages, the dark social traffic that analytics struggles to attribute, so the preview is often the only impression you make.
They also give you control. The og:title can be written for a social audience rather than a search one, and a purpose-made image can carry branding that matches the rest of your marketing.
Common mistakes
- No og:image, or a tiny one. Platforms fall back to a small thumbnail or nothing.
- Relative image addresses. og:image needs the full address, starting https://.
- The same tags on every page. A theme that outputs the homepage’s title and image site-wide makes every shared link look identical.
- Crawlers blocked. If robots.txt or a firewall turns away the platform’s crawler, the preview cannot load.
- Forgetting the cache. Updating tags without refreshing the platform’s stored preview, then assuming the change failed.
- og:locale left as en_US. A small default, but a telling one on a British site.
How to act on it
Paste a few key URLs into Facebook’s Sharing Debugger and LinkedIn’s Post Inspector. Both show what the platform reads and let you refresh its cached preview. If anything is missing, most WordPress SEO plugins, and platforms such as Shopify and Squarespace, let you set a default share image and override the title, description and image page by page.
Give your main service pages and articles their own images rather than relying on one default, write og descriptions that make sense as a standalone sentence, and confirm that og:url matches the canonical tag. Checking these tags across a whole site is part of a technical SEO review, and they work alongside the meta description, which does a similar job in search results.