GlossaryLink unfurler
What is link unfurler?
A link unfurler is the fetcher a chat app or social platform sends to build a preview when someone pastes a link. Slack, Discord, iMessage, WhatsApp and Facebook all have one. Each unfurl is evidence that a person shared your URL somewhere analytics cannot see.
Also called: unfurler, link preview fetcher, unfurl.
Unfurlers look like bots in a log, and most bot lists file them as noise. They are the opposite: an unfurl only happens because a human pasted your link into a conversation. It is the only direct signal of dark social sharing.
One unfurl is not one share. Some apps fetch a preview for every recipient, some cache it, and a link in a busy channel may be unfurled several times. agenttraffic counts unfurls as a floor of shares and lists which URLs were shared where.
iMessage does not have a named unfurler. It sends the same user agents as Facebook (facebookexternalhit and Twitterbot), so those two are reported together as Facebook / iMessage.
Related terms
- Dark social: Dark social is sharing that analytics cannot attribute: links passed in private messages, chat apps, email and text, which arrive with no referrer and get filed under "direct" traffic..
- Floor: A floor is a count reported as "at least this many": the number that could be measured, with the acknowledgement that the true number may be higher.
- User agent string: A user agent string is the text a client sends with every web request to say what it is.
Published 2026-09-21, updated 2026-09-21.