Slack Link Previews

Slack unfurls use Open Graph tags to generate link previews. No special Slack-specific tags needed—just standard OG meta.

<script setup lang="ts">
useSeoMeta({
  ogTitle: 'Dashboard Analytics',
  ogDescription: '847 active users, 12.4% conversion rate',
  ogImage: 'https://app.example.com/og/dashboard.png',
  ogUrl: 'https://app.example.com/dashboard'
})
</script>

Slack reads these four tags. Skip ogUrl if you want—Slack fills it automatically from the shared link.

Image Requirements

Slack displays images at 360x200px in chat, 1200x600px on click. Your OG image should be at least 1200x630px.

useSeoMeta({
  ogImage: 'https://example.com/og-image.png',
  ogImageWidth: 1200,
  ogImageHeight: 630,
  ogImageAlt: 'Dashboard showing 847 active users'
})

Width/height tags help Slack allocate space before download. Alt text appears if image fails.

What Slack Ignores

Slack doesn't care about:

• Twitter Card tags (use those for Twitter/X, not Slack)
• og:type unless you're sharing video/audio
• og:locale
• article:* tags
• Schema.org markup

Don't waste time on tags Slack won't read.

✅ Good for

• SaaS dashboards shared in team channels
• Blog posts in company Slack
• Support docs linked in tickets
• Product pages shared with customers

❌ Don't use for

• Internal tools behind auth (Slack can't access them)
• Pages with dynamic content (Slack caches aggressively)
• Personalized URLs (everyone sees same preview)

Testing

Slack caches unfurls for 30+ days. Testing is painful.

Option 1: URL parameters

https://example.com/page?v=2

Different URL = fresh cache. Increment v each test.

Option 2: Slack Unfurl Tester Visit slack.com/apps/YOUR_APP_ID/event-subscriptions if you have a Slack app. No app? Use URL parameters.

Option 3: Share in DM with yourself Type /unfurl reset https://example.com/page in any channel. Doesn't always work.

Common Issues

Image not showing: Check image size (must be under 5MB), format (PNG/JPG/GIF only), and SSL (HTTPS required). Slack rejects images > 5MB silently.

Wrong description: Slack reads og:description, not meta description. Set both:

useSeoMeta({
  description: 'For search engines',
  ogDescription: 'For Slack/social previews'
})

Old preview stuck: Slack's cache is aggressive. Only fix is URL parameters or waiting 30+ days.

Preview shows but no image: Your og:image URL probably redirects. Slack doesn't follow redirects for images. Use direct image URLs.

Authenticated Pages

Slack's crawler can't log in. Pages behind auth show generic unfurls.

Options:

1. Generate preview pages at public URLs
2. Use signed URLs that expire
3. Accept generic unfurls for private content

Most SaaS apps do option 3. Not worth engineering effort.

Dynamic Content

Slack caches the first unfurl for 30+ days. Users sharing example.com/dashboard all see the same preview, even if dashboard data differs.

Generate unique URLs if previews should differ:

example.com/dashboard?user=alice
example.com/dashboard?user=bob

Overkill for most cases. Static previews work fine.

Related

• Open Graph Tags
• Twitter Cards
• Social Media Images