Fix Notion Page Shared via Slack Showing Broken Preview Image

When you share a Notion page link in Slack, a preview image usually appears to help teammates identify the content at a glance. A broken preview image — showing a gray box or a generic icon — makes the shared link look unprofessional and reduces click-through rates. This problem typically occurs because Slack cannot fetch the correct Open Graph metadata from the Notion page, often due to privacy settings, missing cover images, or caching issues. This article explains why the preview breaks and provides a complete set of steps to restore the intended preview image for any Notion page shared via Slack.

Why Slack Shows a Broken Preview Image for a Notion Page

Slack generates link previews by fetching Open Graph (OG) metadata from the URL you paste. For a Notion page, this metadata includes the title, description, and a preview image. The preview image is taken from the page’s cover image — the large banner at the top of the page. If the page has no cover image, Slack cannot find an OG image and displays a broken or generic placeholder.

Additionally, Slack can only access the metadata of pages that are publicly accessible. If the Notion page is shared exclusively with workspace members or via a private guest link, Slack’s bot may receive a login wall instead of the OG metadata. The bot then falls back to a broken preview or no image at all.

A third cause is Slack’s aggressive link caching. Once Slack has fetched metadata for a URL, it stores that data for up to 24 hours. If you change the cover image or page title after sharing the link, Slack continues to show the old preview — or no preview — until the cache expires or you force a refresh.

Steps to Fix the Broken Preview Image

1. Add or change the cover image on the Notion page
   Open the Notion page in your browser. Hover over the top area of the page and click Add Cover. Choose an image from Notion’s gallery or upload your own. The cover image should be at least 400 by 300 pixels to ensure Slack can generate a clear thumbnail. If a cover image already exists but the preview is broken, replace it with a different image to reset the OG metadata.
2. Publish the page publicly or change share settings
   Click the Share button at the top-right corner of the Notion page. Under Share to web, toggle Public access to On. Slack requires public access to fetch the preview image. If you cannot make the page public due to workspace policies, you must use a different sharing method — private guest links will not generate preview images in Slack.
3. Copy the published link from Notion
   After enabling public access, copy the link shown under Share to web. This URL is different from the internal workspace link. Use this public URL when pasting into Slack. If you previously pasted the internal link, replace it with the public URL.
4. Paste the link in Slack and force a cache refresh
   Paste the public Notion URL into a Slack message. If the preview still appears broken, append ?refresh=1 to the end of the URL and send the message again. For example: https://www.notion.so/your-page-123?refresh=1. This parameter forces Slack to fetch fresh OG metadata instead of using the cached version.
5. Remove and re-paste the link if the preview does not update
   Delete the message containing the link. Wait 30 seconds, then paste the URL again — this time without the ?refresh=1 parameter. Slack will fetch the metadata again from a clean state. The preview image should now appear correctly.

If the Preview Image Still Shows Broken After the Main Fix

Slack cached the old metadata for more than 24 hours

Slack caches link previews for up to 24 hours. If you have followed all steps and the preview remains broken, wait until the cache naturally expires. To speed up the process, you can use the ?refresh=1 trick described above. Some users also report success by pasting the URL in a private channel first, then moving it to the target channel.

The cover image contains unsupported file format or size

Slack supports JPEG, PNG, and GIF images. If your cover image is a BMP, TIFF, or SVG file, Slack cannot use it as a preview. Convert the image to JPEG or PNG and re-upload it to the Notion page. Also ensure the image is at least 400 pixels wide — very small images may be ignored by Slack’s OG parser.

The Notion page is inside a private workspace that blocks external access

Some Notion workspaces have admin settings that prevent any page from being published publicly. If you cannot enable public access, the preview will never work in Slack. In this case, consider sharing a screenshot of the page content directly in Slack, or use Notion’s Share to Slack integration, which sends a formatted message with a preview generated by Notion’s own bot rather than Slack’s OG parser.

Slack workspace policies block external link previews

Some Slack workspaces disable link previews for external domains to improve security or reduce distractions. Ask your Slack workspace admin to check the Settings & Permissions > Link Previews section. If previews are disabled for all external domains, no Notion page will show a preview image regardless of your settings.

Notion Page Sharing Options: Public vs Workspace vs Guest

Sharing Method	Preview Image in Slack	Access Level
Public (Share to web)	Works — OG metadata is fully accessible	Anyone with the link can view the page
Workspace members only	Broken — Slack bot cannot log in	Only members of your Notion workspace
Guest link (private)	Broken — Slack bot cannot authenticate	Specific people invited via email

Only the Public sharing method generates a working preview image in Slack. If your workspace policy or page content prevents public sharing, you will need to use alternative communication methods such as embedding the page content directly in Slack using the Notion Slack integration.

You can now fix a broken preview image for any Notion page shared in Slack. Start by adding a cover image and enabling public access, then paste the public URL with ?refresh=1 to clear Slack’s cache. For persistent issues, check whether your Slack workspace blocks external link previews or whether your Notion workspace restricts public publishing. As an advanced tip, use Notion’s Share to Slack integration from the Share menu to send a formatted message that includes a preview generated by Notion’s own server, bypassing Slack’s OG parser entirely.