You paste your launch link into X, LinkedIn or Slack, and it shows up as a plain grey box. No picture, sometimes the wrong title. On launch day that costs clicks, because people scroll past links without an image.

Here are the six causes I see most often, and a quick way to test each one.

1. There is no og:image tag at all

Social sites do not guess. They read one tag:

<meta property="og:image" content="https://yourproduct.com/og.png">

Test: view the page source (Ctrl+U) and search for og:image. If it is missing, add it in the <head>.

2. The image URL is relative

content="/og.png" works in a browser but many crawlers ignore it. Use the full address with https://.

3. The image is behind a login or blocked

If the file needs a cookie, sits on a staging domain, or your robots.txt blocks the folder, the crawler gets an error page instead of a picture. Open the image URL in a private window. If you cannot see it there, neither can X.

4. The tag is added by JavaScript

Single-page apps often set meta tags after the page loads. Most link crawlers do not run JavaScript, so they never see them. Put the tags in the HTML the server sends, or pre-render the page.

5. Wrong size or too heavy

Use 1200 x 630 pixels (about 1.91:1), PNG or JPG, under 5 MB. Very small images get shown as a tiny thumbnail or not at all. Keep text away from the edges, because some apps crop.

6. The old version is cached

You fixed it, but the preview still looks broken. Social sites cache the first version they saw. LinkedIn has a Post Inspector, and Facebook has a Sharing Debugger, that re-fetch the page. For others, adding a harmless query string (?v=2) to the link usually forces a fresh read.

A five-minute check before launch

  1. View source and confirm og:title, og:description and og:image are there, with full URLs.
  2. Open the image URL in a private window.
  3. Paste the link into a private Slack or Discord message to yourself and look at it.
  4. If anything is off, fix it, then re-fetch with the platform's debugger.

If you want to see all of it at once, I made a free meta tag and share preview checker that shows the Google result and the share card and lists what to fix. No account needed.

What else has broken a link preview for you? I am collecting the weird cases.