Guides › Platforms

Slack link preview: tags, image size and cache refresh

Crawler: Slackbot-LinkExpanding 1.0

Slack "unfurls" links. It first checks for oEmbed, then twitter:* tags, then Open Graph. A large og:image or twitter:image is shown as a big preview.

Extra fields

Slack supports twitter:label1/twitter:data1 (and label2/data2) to show extra key-value lines, such as "Reading time: 4 min".

<meta name="twitter:label1" content="Reading time">
<meta name="twitter:data1" content="4 min">

Refreshing

Slack caches unfurls, so share a variant URL to force a new fetch. Workspace admins can disable unfurls for some domains.

Minimum tags that work everywhere

<meta property="og:title" content="Page title">
<meta property="og:description" content="One or two sentences.">
<meta property="og:image" content="https://example.com/og/page.png">
<meta property="og:url" content="https://example.com/page">
<meta property="og:type" content="website">
<meta name="twitter:card" content="summary_large_image">

Paste your URL into the previewer to see an approximate Slack card and a list of problems.

Related