You added an og:image, but the link preview is blank or wrong on Facebook, X/Twitter, LinkedIn, WhatsApp, or Slack. In almost every case it's one of five specific things — and the most common is that the image URL simply doesn't return HTTP 200. Here's how to find and fix it.
Paste your page into the checker above. If it reports image_broken or image_unreachable, the URL in your og:image tag doesn't load. Open the exact image URL in a private browser tab — if it fails there, the crawler fails too.
Open Graph requires an absolute URL. <meta property="og:image" content="/img/card.png"> is wrong; it must be https://your-site.com/img/card.png.
Facebook, LinkedIn and X aggressively cache. After fixing the tag, re-scrape with the platform's debugger (Facebook Sharing Debugger, LinkedIn Post Inspector) to bust the cache.
Use a PNG or JPG at 1200×630. SVGs and tiny images are often ignored. Keep it under ~5 MB.
If robots.txt or auth blocks the crawler, it can't fetch the image. Make the page and image publicly reachable.
Add OGCheck to CI so a broken preview fails your build before it ships:
python -m ogcheck https://your-site.com/page