Slack unfurl preview checker
Slackbot unfurls links using the favicon, og:site_name, title, description and image.
Tags Slack reads
| Field | Tags, in fallback order |
|---|---|
| Site | og:site_name → favicon |
| Title | og:title → twitter:title |
| Description | og:description → twitter:description |
| Image | og:image → twitter:image |
Image requirements
| Recommended | 1200×630 |
|---|---|
| Minimum | none documented |
| Maximum weight | none documented |
| Formats | JPEG, PNG, GIF |
Card layout
A thumbnail on the right by default. summary_large_image shows a larger image below.
How to refresh the Slack preview cache
Slack caches unfurls for about 30 minutes. Add a query string to force a new fetch.
Common problems
- No unfurl: the page blocks Slackbot in robots.txt, or responds too slowly.
Rule confidence: documented.