Slackbot user agent
Slackbot is the crawler Slack uses to fetch a URL shared in a channel or DM so it can build the message unfurl from Open Graph (and where supported oEmbed) metadata. It is a link-unfurling bot, not a human visit, and identifies itself with a documented Slackbot user-agent token plus a self-identifying URL.
What this means
When a link is posted in Slack, Slack fetches the URL to build the unfurl — the inline preview with a title, description, and image. Slack reads Open Graph and standard meta tags, and uses oEmbed for providers that support it.
The unfurl reflects the metadata Slackbot read, not a human visit. Slack also respects robots.txt for unfurling, so disallowing the Slackbot token suppresses the preview.
How Slackbot identifies itself
Slack's unfurl crawler uses the user-agent token Slackbot, and its user agent contains a self-identifying URL pointing at Slack's documentation. Match on the stable Slackbot token. Slack documents the unfurling behaviour and the tags it reads.
The user agent can be copied like any other, so treat it as a claim. Slackbot reads server-rendered tags and does not execute client-side JavaScript to build the preview.
- User-agent token: Slackbot
- User agent includes a self-identifying Slack URL
- Reads Open Graph / meta tags and oEmbed where available
Debugging a missing unfurl
If a Slack link shows no preview, confirm the page returns 200 with valid Open Graph tags in the initial HTML, and that robots.txt does not disallow the Slackbot token. Login walls and redirects can also block the fetch.
Seeing the Slackbot token in your logs for the shared URL confirms the unfurl fetch reached your server.
How it appears in analytics and logs
A request whose user agent contains the Slackbot token means Slack fetched a URL to render an unfurl. It is triggered by a message and is bot traffic; a small burst when a link is posted is expected, not audience.
Diagnostic use case
Confirm whether Slackbot fetched a shared page, debug a missing or wrong Slack unfurl, and exclude its requests from human analytics.
What WebmasterID can help detect
WebmasterID classifies Slackbot server-side as a social-preview bot and surfaces its fetches on the bot-intelligence view, so unfurl crawls do not inflate human page views or look like referrals.
Common mistakes
- Disallowing Slackbot in robots.txt and then expecting unfurls to render.
- Counting Slackbot unfurl fetches as human visits.
- Relying on JavaScript-injected meta tags Slackbot does not execute.
Privacy and accuracy notes
Slackbot detection uses only the user agent. No human identity is attached to the unfurl fetch. WebmasterID records it as a social-preview bot event, kept out of human analytics.
Frequently asked questions
- Does robots.txt affect Slack unfurls?
- Yes. Slack respects robots.txt for unfurling, so a Disallow targeting the Slackbot token will stop the link preview from rendering for shared URLs on your site.
Related pages
- Twitterbot user agent
Twitterbot is the crawler operated by X (formerly Twitter) to fetch a shared URL and read its Open Graph and Twitter Card metadata so it can render a preview card in a post. It is a link-unfurling bot, not a human visit, and identifies itself with a documented Twitterbot user-agent token.
- Discordbot user agent
Discordbot is the crawler Discord uses to fetch a URL shared in a channel so it can render the embed preview from Open Graph and oEmbed metadata. It is a link-unfurling bot, not a human visit, and identifies itself with a documented Discordbot user-agent token plus a self-identifying URL.
- 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.
- Bot intelligence
Deterministic classification of unfurling and preview bots.
Sources and verification notes
- Slack — Unfurling links in messagesDocuments Slack's unfurl crawler and metadata consumption.
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.