Social preview bot user agents
When someone pastes your link into a social or messaging app, a preview bot fetches the page to build a card from your Open Graph and Twitter Card tags. Bots like facebookexternalhit, Twitterbot, Slackbot, Discordbot, and LinkedInBot identify themselves by token. This page covers what they are and why they hit you.
Why these bots fetch your page
When a link is pasted into a platform, the platform fetches the target URL to build a preview card. It reads Open Graph tags (og:title, og:image, og:description) and Twitter Card tags to populate the card. This fetch happens once per share or per cache refresh, not per human view.
Common preview bots include facebookexternalhit, Twitterbot, Slackbot, Discordbot, and LinkedInBot. Each identifies itself with a recognisable token.
- facebookexternalhit — Facebook/Meta link preview
- Twitterbot — X/Twitter card preview
- Slackbot, Discordbot, LinkedInBot — chat and feed previews
Make sure your tags are served to them
Preview bots typically do not execute JavaScript the way a full browser does, so they rely on server-rendered Open Graph and Twitter Card tags in the initial HTML. If your tags are injected client-side only, previews can come out blank.
Match on the documented token rather than a full version string, and consult each platform's sharing documentation for the exact behaviour and any debugging tools they provide.
How it appears in analytics and logs
A request from a preview-bot token (such as facebookexternalhit or Twitterbot) means someone shared your link and the platform is fetching metadata to render a card. It is bot activity tied to a share, not a human page view.
Diagnostic use case
Recognise link-unfurling bots so preview fetches are counted as bot activity, and confirm your Open Graph and Twitter Card tags are served to them correctly.
What WebmasterID can help detect
WebmasterID classifies social preview bots server-side as social bots, separate from human analytics, so link-unfurl fetches are visible without being mistaken for audience.
Common mistakes
- Counting link-preview fetches as human visits.
- Serving Open Graph tags only via client-side JavaScript, leaving previews blank.
- Blocking preview bots in robots.txt and then wondering why share cards are empty.
Privacy and accuracy notes
Preview bots fetch public metadata; they carry no visitor identity. WebmasterID records the fetch as a bot event and never attaches it to a human profile.
Related pages
- Uptime monitor user agents
Uptime and synthetic monitoring tools repeatedly request your site to check availability and response time. Tools such as UptimeRobot and Pingdom usually identify themselves in the user agent. Their traffic is expected, periodic, and automated. This page explains how to recognise it and keep it out of human analytics.
- Bot vs browser user agents: how to tell them apart
A user-agent string is a self-reported label, not an identity. This page explains how declared bots name themselves, why almost every UA still starts with the legacy Mozilla token, and how to read the difference between an automated client and a real browser without over-trusting the string.
- Bot intelligence
See social, search, and AI bots categorised separately from people.
Sources and verification notes
Last reviewed 2026-06-24. Facts are checked against primary/official sources where available; uncertain specifics are marked “Data not yet verified” rather than guessed.