Slack Link Preview Wrong — How to Fix Slack Unfurl Issues
When you paste a link into Slack, it generates an unfurl — a preview card showing the title, description, and image. If the wrong information is showing, or no preview appears at all, the fix is usually straightforward.
-> Diagnose your Slack unfurl with TryUnfurl
Why Slack Link Previews Go Wrong
Slack reads Open Graph tags from your page when a link is first shared in a channel. It then caches that result. This means:
- If your metadata was wrong at the time of sharing, Slack will show the wrong preview
- If you update your page metadata, Slack won't automatically pick up the changes
- If your page blocks Slack's crawler, no preview will appear
Step-by-Step Fix
Step 1 — Verify your metadata is correct
Paste your URL into TryUnfurl.com — it shows exactly what Slack reads from your page. If TryUnfurl shows the correct title, description, and image, the problem is Slack's cache, not your metadata. If TryUnfurl shows wrong or missing data, fix your Open Graph tags first.
Step 2 — Fix your Open Graph tags (if needed)
Slack reads these tags from your page's HTML <head>:
<meta property="og:title" content="Your Page Title">
<meta property="og:description" content="Your page description.">
<meta property="og:image" content="https://yourdomain.com/og-image.jpg">
<meta property="og:image:width" content="1200">
<meta property="og:image:height" content="630">
Make sure og:image is an absolute HTTPS URL pointing to a publicly accessible image.
Step 3 — Clear Slack's cached preview
Slack doesn't have a public cache-clearing tool. Your options:
- Delete the original message containing the link and re-paste it — Slack will fetch fresh metadata when the link is shared again
- In some workspaces, hover over the unfurl preview to see a refresh icon — click it to force a re-fetch
- Wait — Slack's cache typically expires within a few hours
Slack Unfurl Troubleshooting Table
| Symptom | Likely cause | Fix |
|---|---|---|
| No preview appears at all | Page has no OG tags, or Slackbot is blocked | Add og:title, og:description, og:image; check robots.txt |
| Wrong title showing | Cached old metadata, or conflicting tags | Fix OG tags; delete and re-share |
| Wrong image showing | Cached old og:image, or multiple og:image tags |
Fix OG image URL; delete and re-share |
| No image in preview | og:image missing, wrong URL, or too small |
Use 1200 × 630 px absolute HTTPS image |
| Preview worked before, now blank | Page moved, returns 4xx/5xx, or Slackbot now blocked | Check URL is accessible; check server logs |
| Correct tags in source but Slack shows wrong data | JavaScript rendering — Slack doesn't execute JS | Use SSR or SSG to inject OG tags in initial HTML |
| Preview image is tiny | Image below minimum size | Use 1200 × 630 px image |
What Slack's Crawler Looks For
Slack's bot (Slackbot) reads metadata in this order:
og:title→ falls back to<title>og:description→ falls back to<meta name="description">og:image→ falls back to first image on page (unpredictable)og:site_name
Slack does not execute JavaScript. If your site uses a React, Vue, or Angular SPA without server-side rendering, Slackbot will see an empty page and either show no preview or show a very minimal one.
Is Slackbot Being Blocked?
If previews work for some links but not yours, check that Slackbot isn't being blocked:
- robots.txt — ensure
Slackbotisn't disallowed - Cloudflare or other WAF — aggressive bot protection can block Slackbot; add an exception for
Slackbotuser-agent - IP allowlisting — Slack's crawler IPs are not publicly published; IP-based blocking will prevent previews
Slack Image Requirements
| Requirement | Value |
|---|---|
| Recommended size | 1200 × 630 px |
| Minimum size for large display | 500 × 262 px |
| URL type | Absolute HTTPS only |
| Must be public | Yes — not behind auth or blocked by robots.txt |
Check Your Slack Preview
Paste your URL into TryUnfurl.com to see a Slack-style preview and the full metadata Slackbot will read — before you share anything.