Use it alongside Facebook’s Sharing Debugger
Facebook’s own Sharing Debugger (opens in a new tab) shows what Facebook’s crawler scraped and can make it scrape your page again. Use it for the final word, because this checker is independent of Facebook and its preview is an approximation.
This checker answers the question that comes before that: what’s wrong with the page, and what exactly should you change? It scores your tags, measures your image, gives you snippets for your framework and shows the same link on seven other platforms.
The tags Facebook reads
Facebook builds its card from Open Graph tags. Without them, it has to guess from your <title>, your meta description and the page content. Add these to your <head>:
<meta property="og:url" content="https://example.com/blog/my-post">
<meta property="og:type" content="article">
<meta property="og:title" content="Your page title">
<meta property="og:description" content="One or two sentences about the page.">
<meta property="og:image" content="https://example.com/images/card.jpg">
<meta property="og:image:width" content="1200">
<meta property="og:image:height" content="630">The width and height tags let Facebook lay out the image before it has downloaded the file, which helps the first share of a new page. Facebook’s documentation also lists fb:app_id, which connects the page to a Facebook app. The Debugger may mention it, but you need it only if you use Facebook’s app features.
Image size rules
- Recommended: 1200×630, a 1.91:1 ratio. Facebook advises at least 1080 pixels wide for high-resolution screens.
- Small thumbnail: an image below 600×315 appears as a small square beside the text.
- No image: an image below 200×200 isn’t shown.
- File size: keep it under 8 MB. A smaller file is better, since other platforms are stricter.
Facebook shows up to about 100 characters of title and 160 of description, often fewer on a phone, so put the important words first. The cheat sheet compares these limits across platforms.
Why your Facebook preview is wrong
- The old image keeps appearing: Facebook caches images by URL and won’t update one until the URL changes. Upload the new image under a new file name, then update
og:image. - The wrong image appears:
og:imageis missing, so Facebook picked one from the page. - There’s no image: the URL may be relative, the file too small, or the format unsupported, such as SVG. The health report tells you which.
- Facebook can’t reach the page: a firewall or bot filter may be blocking
facebookexternalhit. Facebook advises adding its user agent or IP addresses to your allow list. Our checker uses its own user agent, so a pass here doesn’t prove Facebook gets through. The Debugger will show that. - The tags are added by JavaScript: link preview crawlers don’t run it, so the tags must be in the HTML your server sends.
Refreshing a preview Facebook has cached
Facebook refreshes scraped data on its own schedule, which its documentation describes as a 24-hour cycle. To update it sooner, paste your URL into the Sharing Debugger and ask it to scrape again. You can do the same before you publish a post so the first people to share the link see the right card. Then check your page again to confirm the tags are right.