OG CHECKER

Check how your link looks in Slack

Slack "unfurls" links automatically when pasted in channels and DMs. A well-configured OG setup means your product pages, docs, and blog posts look polished when your team or customers share them. Slack reads standard Open Graph tags but also supports some unique behaviors around twitter:card and favicons.

How Slack Renders Link Previews

When someone pastes a link in Slack, the Slackbot crawler fetches the URL and generates an unfurl card:

  1. og:title — the bold headline of the unfurl. Falls back to <title> if missing.
  2. og:description — the text block under the title. Falls back to meta[name=description].
  3. og:image — the preview image displayed alongside the text. Slack renders this as a thumbnail on the right or a large image below, depending on its dimensions.
  4. og:site_name — shown in gray above the title as the source label. This is especially visible in Slack.
  5. favicon — Slack displays the site favicon next to the site_name label.

Slack caches unfurls for approximately 30 minutes in most workspaces, making it one of the fastest platforms to reflect OG changes. However, previously unfurled links in existing messages won't update automatically.

Slack Image Requirements

Recommended Size1200x630 px
Aspect Ratio1.91:1
Max File Size5 MB
FormatsJPG, PNG, GIF (no SVG)

Images wider than ~400 px render as large inline previews. Narrower or square images appear as small thumbnails on the right side of the unfurl.

Slack OG Tag Tips

  1. 1Always set og:site_name. Slack displays it prominently as a gray label above the title — it's your brand name in every unfurl. Without it, Slack uses the domain, which looks less professional.
  2. 2Slack displays images in two modes: thumbnail (small, right-aligned) for square/portrait images, and inline (large, below text) for landscape images wider than ~400px. Use landscape images (1200x630) if you want maximum visual impact.
  3. 3Keep og:description to 2-3 lines (~150 characters). Slack truncates longer descriptions and shows a "Show more" link, which most users won't click.
  4. 4Make sure your site has a high-quality favicon. Slack shows it at 16x16 or 32x32 next to your site name — a pixelated or missing favicon makes unfurls look amateurish.
  5. 5Slack re-fetches pages relatively quickly (~30 minute cache). But if a link was already unfurled in a conversation, the cached version persists in that message. To refresh, delete and re-paste the link.
  6. 6For internal tools and documentation sites, ensure Slack's crawler (Slackbot-LinkExpanding) is not blocked by authentication. Slack does not honor robots.txt — authentication is the only way to block its crawler, and the #1 reason unfurls fail in Slack. See our guide on how to fix broken link previews.
  7. 7If you use twitter:card with summary_large_image, Slack will display the image in large inline format. This is a good trick to force the large image layout even if your OG image dimensions are borderline.
  8. 8Avoid setting og:image to an SVG file. Slack's renderer doesn't support SVG for unfurl images and will show no image at all.
  9. 9Need to check other platforms? Try our Twitter, LinkedIn, Facebook, WhatsApp, or Discord checkers.

Check other platforms

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Paste any URL to get an instant audit with score, social previews, and a prioritized fix list.