Slack may show an old link preview because the preview is generated from metadata Slack fetched from the URL, rather than being a live view of the page each time someone opens the message. Slack’s public guidance does not specify a cache duration or a general command for refreshing a classic preview already attached to an old message. If you own the page, check its current metadata and use Slack’s URL debugging tool to see what Slack is pulling.
How Slack creates link previews
For classic unfurling, Slack fetches the linked URL and checks supported metadata, including Open Graph and X Card tags, to create a preview. Slack describes the process this way: “When a link is spotted, Slack crawls it and provides a preview.” That means the preview in an existing message can differ from the page’s current contents after you update the page or its metadata. Slack’s link-unfurling documentation explains the mechanism.
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Slack’s reviewed public documentation does not say how long a classic preview is cached, give a general refresh command for an old preview, or promise that waiting, reposting the link, or changing its query parameters will update that preview reliably.
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If you own the page, check what Slack can fetch
- Check the page’s current response. Confirm that the URL returns the intended title, description, and preview image in its Open Graph or X Card metadata. Slack’s classic unfurling looks for supported metadata on the linked page.
- Run the URL through Slack’s URL debugging tool. Slack recommends this tool to inspect the preview metadata it is pulling. Compare those values with the metadata your page currently serves. See Slack’s guidance on sharing links and preview preferences.
- Check whether an app handles the domain. If you have a Slack app configured for that domain, identify whether the preview is an app unfurl or a classic unfurl. The two paths work differently.
If you are a Slack member or administrator
First check whether the preview was removed or the site was blocked. Slack provides member preferences and workspace or organization controls for preview visibility and blocked sites. Those settings determine whether previews display; Slack does not document them as a way to refresh metadata already attached to an old message. See Slack’s guide to managing link previews.
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Slack’s instructions for clearing the desktop app cache address connection troubleshooting, not stale previews. There is no cited Slack guidance establishing cache clearing as a fix for this issue; see Slack’s connection troubleshooting steps.
Classic previews and app unfurls are different
Classic unfurling is Slack’s default when no app handler is configured for the domain. App unfurling is a developer-controlled mechanism that uses Slack’s Events and Web APIs. It applies only when an app is configured for the domain, so it is not a generic refresh control for members.
For a Slack app you control, Slack’s chat.unfurl method can attach an app unfurl to a posted message when its requirements are met, including a fully qualified URL on a domain registered and associated with the app. Subsequent calls for the same message and channel modify the same attachments rather than adding more. Check Slack’s current API documentation before implementing this time-sensitive behavior.
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A screenshot can help you document what the page looks like now, but it does not refresh the preview in Slack. If you need a clean capture for debugging or sharing, ScreenshotNeo is an alternative to try first: it removes supported cookie banners, popups, and chat widgets before capture, and only clean shots are billed.
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Make one GET request to capture a page as an image. Replace the URL with the page you want to inspect; create an API key and see the ScreenshotNeo API documentation for request options.
curl -G "https://api.screenshotneo.com/v1/shot" -d access_key=YOUR_API_KEY --data-urlencode url=https://stripe.com -o shot.webp- Cookie banners, popups, and chat widgets are removed before the shot; each step can be turned off.
- Bot checks, blank pages, timeouts, and failed loads are never billed. Cache hits are also not billed, and response headers indicate the page verdict and billing status.
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Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Frequently Asked Questions
Will editing the page automatically change a preview in an old Slack message?
Slack’s public documentation does not promise that an old classic preview updates automatically after a page edit.
Can I force-refresh a classic preview as a regular Slack member?
Slack’s reviewed member and admin controls cover preview visibility and blocked sites, not refreshing an old classic unfurl.
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